Fuel injection control device

ABSTRACT

A fuel injection control device (ECU) for controlling injection supply of fuel to a target engine has a program for sequentially sensing fuel pressure fluctuating with injection of a predetermined injector a program for detecting an injection centroid of a diagram as a profile of a transition of an injection rate of the injector at a present time based on a transition of the sequentially sensed fuel pressure, and a program for varying an injection command (injection timing) of the injector based on the detected injection centroid and an injection centroid of a predetermined basic diagram such that a relative positional relationship between the injection centroids of the diagram as the actual profile of the injection rate transition and the basic diagram becomes a relationship, in which timings of the injection centroids are close to each other.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2007-227121 filed on Aug. 31, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fuel injection control device that is applied to a fuel supply system injecting fuel through a predetermined injector and that controls a fuel injection characteristic of the system.

2. Description of Related Art

As one of technologies for improving emission of an in-vehicle diesel engine or the like, there is a known technology (high-pressure injection) for injecting and supplying fuel, which is pressurized to high pressure, directly into a cylinder through an injector. In recent years, a common rail fuel injection system (for example, a system described in Patent document 1: JP-A-H10-220272) has come to attract attention as a fuel injection system realizing the high-pressure injection. In the system, the fuel pumped from a fuel pump is accumulated in a common rail in a high-pressure state, and the accumulated high-pressure fuel is supplied to the injectors of respective cylinders through pipes (high-pressure fuel passages) provided to the respective cylinders. In the system, a predetermined pressure sensor (a rail pressure sensor) is provided to the common rail. The system is configured to control drive of various devices constituting a fuel supply system based on an output (a sensor output) of the rail pressure sensor.

Conventionally, in the case where an injection operation of the injector is controlled with such the common rail fuel injection system, a control method of setting an injection pattern in accordance with an engine operation state of each time with reference to a map (an adaptation map), in which an injection pattern (i.e., an adaptation value) for each engine operation state is written, or a mathematical expression is widely adopted. The device stores the optimum pattern (i.e., the adaptation value), which is beforehand obtained for each anticipated engine operation state through experiment and the like, as the map, the mathematical expression or the like (in ROM, for example). Thus, the device sets the injection pattern corresponding to the engine operation state with reference to the map, the mathematical expression or the like.

Thus, fuel supply to the engine can be performed in an injection mode (i.e., the injection pattern) suitable for the engine operation state of each time by using the map, in which the adaptation values are written, or the mathematical expression. However, when mass production and mass marketing of respective components of the engine control system are performed, usually, there occur certain individual differences in characteristics of various kinds of control components including the injector, for example, between the engines and also between the cylinders in the case of a multi-cylinder engine. In such the case, it takes a lot of works and is not realistic for the present production system to obtain the adaptation values (the optimum injection patterns) for all the components (for example, all the cylinders manufactured through the mass production and mounted in the vehicle) in consideration of also the individual differences. Therefore, it is difficult to perform the control in consideration of all the influences due to the individual differences even when the map, in which the adaptation values are written, or the mathematical expression is used.

In order to perform the injection control with high accuracy, a characteristic change resulting from aging of the control components and the like is not negligible. Even if the conventional device such as the device described in Patent document 1 can obtain the optimum value with high accuracy in an initial stage, an influence of the subsequent characteristic change is unknowable. Therefore, there is a concern that there occurs a deviation from the optimum value with passage of time. In this case, an adaptation value of a degradation factor (a coefficient concerning a degree of degradation with time) may be beforehand obtained with an experimental value and the like and may be stored as a map, a mathematical expression or the like. However, there is also the above-mentioned individual difference in the temporal characteristic change of every component. Therefore, it is difficult to thoroughly remove the influence.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a fuel injection control device capable of performing appropriate fuel injection control in accordance with an injection characteristic of each time including a characteristic change with time.

According to an aspect of the present invention, a fuel injection control device is applied to a fuel supply system that injects fuel to an inside of a cylinder as a part of a target engine for performing fuel combustion an intake passage of the engine or an exhaust passage of the engine with a predetermined injector. The fuel injection control device includes a fuel pressure sensing section an injection centroid detecting section, and an injection varying section. The fuel pressure sensing section sequentially senses fuel pressure fluctuating with the injection of the injector. The injection centroid detecting section detects an injection centroid as a geometric centroid of a diagram as a profile of a transition of an injection rate at a present time based on a transition of the fuel pressure sequentially sensed by the fuel pressure sensing section. The injection rate is equivalent to a fuel quantity injected from the injector per unit time. The injection varying section varies an injection command to the injector or an injection condition of the injector based on the injection centroid detected by the injection centroid detecting section and an injection centroid of a predetermined basic diagram such that a relative positional relationship between the injection centroid of the diagram as the actual profile of the injection rate transition and the injection centroid of the basic diagram becomes a predetermined relationship.

The inventors invented the above-described device by paying an attention to a phenomenon that injection characteristics (output torque, emission characteristics and the like of a target engine) changes if a geometric centroid (hereinafter, referred to as an injection centroid) of a diagram as a profile of an injection rate transition differs even when the injection is performed with the same injection quantity. That is, with this device, the injection centroid of the diagram as the present profile of the injection rate transition can be detected with the injection centroid detecting section. Also, the injection command to the target injector or the injection condition of the injector can be varied with the injection varying section such that a relative positional relationship between the injection centroid of the diagram as the actual profile of the injection rate transition and the injection centroid of the basic diagram becomes a predetermined relationship in the same combustion cycle or in a subsequent combustion cycle. With such the construction, the injection command, the injection condition, and eventually the position of the injection centroid is adjusted in accordance with the injection characteristic of each time, thereby enabling appropriate fuel injection control.

According to another aspect of the present invention, the injection varying section varies the injection command to the injector or the injection condition of the injector to approximate timings of the injection centroids of the diagram as the actual profile of the injection rate transition and the basic diagram to each other. In addition to the construction or alternatively, according to another aspect of the present invention, the injection varying section varies the injection command to the injector or the injection condition of the injector to approximate values of the injection rates at the injection centroids of the diagram as the actual profile of the injection rate transition and the basic diagram to each other.

Thus, the injection characteristics (output torque, emission characteristics and the like of the target engine) are improved with either construction. Through the experiments or the like by the inventors, it was found that the construction of matching the timings of the injection centroids gives a better effect of improving the injection characteristics than the construction of matching the injection rates at the injection centroids between the both diagrams.

According to another aspect of the present invention, the injection varying section adjusts at least one of injection start timing and injection end timing of the injector by varying the injection command to the injector or the injection condition of the injector, thereby approximating the timings of the injection centroids of the diagram as the actual profile of the injection rate transition and the basic diagram to each other. Thus, the timing of the injection centroid can be adjusted more easily and appropriately.

According to another aspect of the present invention, the injection varying section adjusts both of the injection start timing and the injection end timing of the injector at a predetermined ratio (e.g., a ratio of 1:1, 3:7, 1:9 or 1:−1) therebetween. Thus, the timing of the injection centroid can be adjusted more easily and appropriately. In this case, if the entire diagram is adjusted in addition to the adjustment of both of the injection start timing and the injection end timing at the ratio of 1:1, the timing of the injection centroid moves by the same displacement amount as each timing. Eventually, the timing of the injection centroid can be adjusted in a simple manner.

However, in these cases, if the injection execution timing (i.e., the injection start timing) is changed without limitation, ignition timing will deviate largely from a reference value (i.e., an originally anticipated value), and as a result, there occurs a possibility of causing an unexpected situation (i.e., a phenomenon not checked by the experiment or the like). Therefore, according to another aspect of the present invention, the injection varying section adjusts the injection start timing within a predetermined adjustment range, and the fuel injection control device further includes an ignition timing detecting section and an adjustment range varying section. The ignition timing detecting section detects ignition timing concerning the injection performed at the injection start timing. The adjustment range varying section variably sets the adjustment range based on the ignition timing detected by the ignition timing detecting section. Thus, the timing of the injection centroid can be adjusted while maintaining the ignition timing within the appropriate range. As a result, reliable injection control can be realized.

According to another aspect of the present invention, the ignition timing detecting section obtains a time from the injection start to the ignition based on the injection start timing as an ignition delay and detects the ignition timing of the same injection based on the ignition delay. With such the construction, by using a predetermined map, a mathematical expression or the like, the above-described ignition timing can be detected relatively accurately and easily.

According to another aspect of the present invention, the fuel injection control device variably controls the value of the injection rate at the injection centroid by using a direct acting injector such as a direct acting piezo injector, which has been developed in recent years, based on an injection command to the injector. However. such the injector has not spread sufficiently. It is difficult to freely control the injection rate in a general injector based on only the injection command. Therefore, according to another aspect of the present invention, the injection varying section varies injection pressure of the injector as the injection condition.

The diagram as the profile of the injection rate transition changes in accordance with the injection pressure of the injector. With the device according to the above aspect of the invention, the diagram as the actual profile of the injection rate transition can be varied by varying the injection pressure of the injector.

If the injector has multiple types of switchable injection holes (for example, multiple injection holes having different shapes), the injection pressure of the injector may be varied by switching the injection holes. When the injector has a pressure intensifying mechanism, the injection pressure of the injector may be varied by operating the pressure intensifying mechanism.

In the case where the present invention is applied to a general injector, following constructions are specifically effective. That is, according to another aspect of the present invention, the injection varying section varies the injection pressure of the injector by varying a pumping quantity of a fuel pump that performs pumping supply of the fuel to the injector. According to another aspect of the present invention, the injection varying section varies the injection pressure of the injector by varying pumping timing of the fuel pump that performs pumping supply of the fuel to the injector. According to another aspect of the present invention, the injection varying section varies the injection pressure of the injector by varying a valve opening degree of a pressure reducing valve provided to the injector or to a fuel supply passage of the injector.

According to another aspect of the present invention, the fuel injection control device further includes an injection centroid determining section for determining whether a deviation amount between a position of the actual injection centroid and a position of the injection centroid of the predetermined basic diagram is greater than a permissible level. When the injection centroid determining section determines that the deviation amount between the positions of the injection centroids is greater than the permissible level, the injection varying section varies the injection command to the injector or the injection condition of the injector such that a relative positional relationship between the injection centroids of the diagram as the actual profile of the injection rate transition and the basic diagram becomes a predetermined relationship.

With such the construction, the above-mentioned positional adjustment of the injection centroid is performed only when the deviation amount of the position of the injection centroid is greater than the permissible level. As a result, the positional adjustment can be performed efficiently.

According to another aspect of the present invention, the fuel injection control device further includes a maximum injection rate sensing section for sensing an injection rate at the time when the injection rate is maximized in the injection based on the transition of the fuel pressure sequentially sensed by the fuel pressure sensing section. The injection rate is equivalent to a fuel quantity injected from the injector per unit time. The injection centroid determining section determines whether the deviation amount between the injection centroids of the both diagrams is greater than the permissible level based on whether a deviation amount between the maximum injection rate sensed by the maximum injection rate sensing section and the maximum injection rate of the basic diagram is greater than another permissible level.

When the maximum injection rate of the diagram is deviated, the injection centroid of the diagram is also deviated. Therefore, with the above construction, the injection centroid determining section can be realized more easily and appropriately. It is effective to provide the maximum injection rate sensing section as a section that senses the maximum injection rate in the injection based on the (maximum) fuel pressure decrease amount due to the target injection in the fuel pressure transition sequentially sensed by the fuel pressure sensing section, for example.

According to another aspect of the present invention, the basic diagram includes one of a triangle, a trapezoid and a rectangle or a diagram made by combining multiple pieces of at least one kind of the triangle, the trapezoid and the rectangle.

When a general injector is adopted, a diagram as a profile of an injection rate transition of the injector corresponds to either one of the above-described diagrams. Therefore, such the construction is effective when the general injector is adopted in the device according to one of the above aspects of the present invention.

According to another aspect of the present invention, the fuel injection control device further includes a basic diagram varying section for variably setting at least one of the basic diagram and a parameter of the basic diagram in accordance with a predetermined parameter. For example, the predetermined parameter is a fuel injection condition such as injection pressure or request torque based on an engine operation state such as engine rotation speed or an operation manipulation by an operator.

With such the construction, the basic diagram and the parameters of the basic diagram can be changed in accordance with the situation of each time, and eventually, the above-described device can be realized in a more practical form. The basic diagram varying section can be easily and appropriately realized by using a map or the like.

The device according to any of the above aspects adjusts the injection centroid of the diagram as the profile of the injection rate transition. However, a construction of adjusting the maximum injection rate in place of or in addition to the injection centroid can exert similar effects. That is, according to another aspect of the present invention, the fuel injection control device is applied to a fuel supply system that injects fuel to an inside of a cylinder as a part of a target engine for performing fuel combustion, an intake passage of the engine or an exhaust passage of the engine with a predetermined injector. The fuel injection control device has a fuel pressure sensing section, a maximum injection rate sensing section, and an injection varying section. The fuel pressure sensing section sequentially senses fuel pressure fluctuating with the injection of the injector. The maximum injection rate sensing section senses an injection rate at the time when the injection rate is maximized in the injection based on a transition of the fuel pressure sequentially sensed by the fuel pressure sensing section. The injection rate is equivalent to a fuel quantity injected from the injector per unit time. The injection varying section varies an injection command to the injector or an injection condition of the injector based on the maximum injection rate sensed by the maximum injection rate sensing section to approximate the maximum injection rate of the actual injection to a predetermined reference value. With such the construction, the injection command, the injection condition, and eventually the maximum injection rate are adjusted in accordance with the injection characteristic of each time, thereby enabling appropriate fuel injection control.

A construction enabling adjustment of both of the injection centroid and the maximum injection rate is more effective and preferable. For example, according to another aspect of the present invention, the fuel injection control device is applied to a fuel supply system that injects fuel to an inside of a cylinder as a part of a target engine for performing fuel combustion. an intake passage of the engine or an exhaust passage of the engine with a predetermined injector. The fuel injection control device has a fuel pressure sensing section, an injection centroid detecting section, a maximum injection rate sensing section, and an injection varying section. The fuel pressure sensing section sequentially senses fuel pressure fluctuating with the injection of the injector. The injection centroid detecting section detects an injection centroid as a geometric centroid of a diagram as a profile of a transition of an injection rate at a present time based on a transition of the fuel pressure sequentially sensed by the fuel pressure sensing section. The injection rate is equivalent to a fuel quantity injected from the injector per unit time. The maximum injection rate sensing section senses an injection rate at the time when the injection rate is maximized in the injection based on a transition of the fuel pressure sequentially sensed by the fuel pressure sensing section. The injection varying section adjusts at least one of the injection centroid of the diagram as the actual profile of the injection rate transition and the maximum injection rate of the actual injection by variably setting the injection command to the injector or the injection condition of the injector based on the injection centroid detected by the injection centroid detecting section and the maximum injection rate sensed by the maximum injection rate sensing section. With such the construction, the injection centroid and the maximum injection rate (or only either one of them) can be adjusted appropriately in a mode suitable for the situation at the present time based on the injection centroid and the maximum injection rate sensed at the present time.

In this case, according to another aspect of the present invention, the injection varying section adjusts one of the injection centroid of the diagram as the actual profile of the injection rate transition and the maximum injection rate of the actual injection and then adjusts the other one. With such the construction, the adjustment of not only either one of the injection centroid and the maximum injection rate but also both of them is possible. Thus, appropriate fuel injection control can be performed.

Alternatively, according to another aspect of the present invention, the injection varying section selects one of the injection centroid of the diagram as the actual profile of the injection rate transition and the maximum injection rate of the actual injection as an adjustment target at the present time based on the injection centroid detected by the injection centroid detecting section and the maximum injection rate sensed by the maximum injection rate sensing section and adjusts the one selected as the adjustment target by variably setting the injection command to the injector or the injection condition of the injector. With such the construction, one of the injection centroid and the maximum injection rate can be selected as the adjustment target at the time. Eventually, efficient fuel injection control can be realized in accordance with the situation of each time.

According to another aspect of the present invention, the injection varying section varies the injection command to the injector by updating a correction coefficient for a predetermined reference map, in which the injection command used when the injection control is performed with the injector is written. With such the construction, the injection command to the injector can be varied easily and appropriately.

According to another aspect of the present invention, the injection varying section produces the injection command to the injector such that an injection result obtained based on the fuel pressure transition sequentially sensed with the fuel pressure sensing section during a present combustion cycle of the target engine is reflected in an injection in a subsequent combustion cycle. By continuously performing the production of the injection command while applying such the feedback to the injection command, appropriate fuel injection can be performed over a long period of time.

According to another aspect of the present invention, the injection varying section uses a pressure transition sensed up to a present time in a combustion cycle of the target engine based on the fuel pressure transition sequentially sensed by the fuel pressure sensing section to produce the injection command to the injector about a predetermined operation concerning the fuel injection of the injector to be performed after the present time in the same cycle.

Thus, by adjusting the subsequent injection operation based on the pressure transition sensed previously while sensing the injection characteristic (equivalent to pressure transition) with high simultaneity (i.e., in real time), the error at the previous timing can be compensated. For example, a construction that the predetermined operation concerning the fuel injection is a valve closing operation of the injector is effective. With such the construction, the valve closing timing of the injector can be adjusted in accordance with the error of the area of the detected diagram (i.e., the injection quantity) up to the present time. Eventually, the injection quantity error resulting from the deviation in the area of the detected diagram can be compensated to maintain the fuel injection quantity at the time to be appropriate.

According to another aspect of the present invention, the injector has a fluid control valve for controlling an inflow of a fluid to a predetermined space and an outflow of the fluid from the same space and a needle that performs reciprocation operation inside a valve body of the injector in accordance with a change in pressure in the space accompanying the inflow and the outflow of the fluid to open and close an injection hole or a fuel supply passage extending to the injection hole, thereby performing valve opening and valve closing of the injector.

According to another aspect of the present invention, the injector has a needle that performs predetermined reciprocation operation inside a valve body of the injector to open and close an injection hole (fuel injection hole) or a fuel supply passage extending to the injection hole, thereby performing valve opening and valve closing of the injector. The injector continuously varies a reciprocation movement amount of the needle in accordance with the injection command to the injector.

According to another aspect of the present invention, the fuel supply system is a fuel injection system that has a pressure accumulator for accumulating the fuel to be supplied to the injector under pressure and at least one fuel pressure sensor for sensing pressure of the fuel flowing through an inside of a fuel passage extending from the pressure accumulator to a fuel injection hole of the injector at a predetermined point downstream of a neighborhood of a fuel discharge hole of the pressure accumulator with respect to a fuel flow direction. The fuel pressure sensing section sequentially senses the fuel pressure based on at least one output of the at least one fuel pressure sensor.

In this way, the above-described fuel pressure sensor is installed to measure the pressure at a predetermined point downstream of a neighborhood of the fuel discharge hole of the pressure accumulator with respect to the fuel flow direction in the fuel passage extending from the pressure accumulator to the fuel injection hole of the injector. Thus, the pressure fluctuation mode due to at least one of the injection operation of the injector concerning a predetermined injection and the actual injection can be sensed appropriately at the installation position of the sensor. The injection operation of the injector is, for example, an opening/closing action of an electromagnetic valve in the case of an injector that drives a needle based on opening and closing of the electromagnetic valve. The actual injection is the injection actually performed through the injection operation.

The device described in Patent document 1 described above fundamentally controls the injection pressure of the injector only with a rail pressure sensor that senses the pressure (i.e., the rail pressure) in the common rail as the pressure accumulator. In this device, the pressure fluctuation due to the injection (including the injection operation) attenuates when or before the fluctuation reaches from the fuel injection hole of the injector to the common rail and does not appear as a fluctuation of the rail pressure. Therefore, with such the device, it is difficult to sense the pressure fluctuation caused by the above-described injection with high accuracy.

As contrasted thereto, the device according to the above aspect of the present invention has the fuel pressure sensor that senses the injection pressure at the position closer to the fuel injection hole than the rail pressure sensor (or a sensor provided near the common rail) is. Therefore, the pressure fluctuation due to the injection (including the injection operation) can be grasped appropriately with the pressure sensor before the pressure fluctuation attenuates. Therefore, with such the device, the injection characteristic can be adjusted appropriately with the injection varying section in accordance with the injection characteristic of each time based on the fuel pressure sequentially sensed with the fuel pressure sensing section. Thus, suitable fuel injection control can be performed.

Moreover, in some cases, the fuel injection control device constituting a common rail type fuel injection system is provided with a fuel pulsation reducing device in a connection between the common rail and a fuel discharge pipe of the common rail for reducing a fuel pulsation transmitted to the common rail through the fuel discharge pipe in order to reduce the pressure pulsation in the common rail and to supply the fuel to the injector at stable pressure. In such the cases, the pressure fluctuation due to the injection (including the injection operation) arises in the fuel injection hole of the injector and spreads toward the common rail through the common rail fuel discharge pipe. The fuel pulsation out of the pressure fluctuation is reduced (attenuated) by the fuel pulsation reducing device. In such the construction, it is difficult to correctly sense the pressure fluctuation mode due to the injection (including the injection operation) based on the pressure in the common rail (i.e., the rail pressure).

In regard to this point, according to another aspect of the present invention, the fuel injection control device is applied to a fuel injection system that has the fuel pulsation reducing device and at least one fuel pressure sensor for sensing pressure of the fuel flowing through an inside of a fuel passage extending from the pressure accumulator to a fuel injection hole of the injector at a predetermined point downstream of the fuel pulsation reducing device with respect to a fuel flow direction. The fuel pressure sensing section sequentially senses the fuel pressure based on at least one output of the at least one fuel pressure sensor. With such the construction, the pressure fluctuation mode can be sensed with the fuel pressure sensor before the fuel pulsation is reduced by the fuel pulsation reducing device. Eventually, the pressure fluctuation mode can be sensed with high accuracy.

In this case, according to another aspect of the present invention, the fuel pulsation reducing device is constituted by an orifice (a restrictor), a flow damper, or a combination of the orifice and the flow damper. With such the construction, the above object can be attained appropriately. Moreover, since the technology for reducing the fuel pulsation with the use of the orifice or the flow damper has been already put in practical use and has actual achievements, thereby possessing high practicality and reliability.

According to another aspect of the present invention, at least one of the fuel pressure sensors is provided inside the injector or near the injector.

The pressure fluctuation mode due to the injection (including the injection operation) can be sensed through the sensor output of the pressure sensor at higher accuracy as the installation position of the fuel pressure sensor is closer to the fuel injection hole of the injector. Therefore, in order to sense the pressure fluctuation mode with high accuracy, it is effective to install the fuel pressure sensor inside or near the injector as in the construction according to the above aspect. In this case, if at least one of the fuel pressure sensors is provided in a fuel inlet of the injector, mountability and maintenance performance of the fuel pressure sensor are improved and the pressure can be sensed with high accuracy in a comparatively stable manner.

According to another aspect of the present invention, at least one of the fuel pressure sensors is provided at a position in the fuel discharge pipe of the pressure accumulator closer to the fuel injection hole of the injector than the pressure accumulator. In the device according to the above aspects using the fuel pressure sensor(s), it is important to locate at least one of such the sensors at a position, which is provided closer to the injector than the pressure accumulator to the extent that the pressure fluctuation caused in the injector does not attenuate completely before reaching the position. For this reason, it is desirable to locate the fuel pressure sensor at the position close to the injector.

According to another aspect of the present invention, the fuel pressure sensing section sequentially obtains a sensor output of the fuel pressure sensor at an interval short enough to create a profile of a pressure transition waveform with the sensor output.

The pressure fluctuation mode due to the injection (including the injection operation) can be usually sensed as a pressure transition waveform. In order to sense the pressure transition waveform (i.e., the pressure fluctuation mode) appropriately with high accuracy, it is effective to sequentially obtain the sensor output of the fuel pressure sensor at an interval short enough to grasp the pressure transition waveform. For example, according to yet another aspect of the present invention, the fuel pressure sensing section sequentially obtains the sensor output of the fuel pressure sensor at an interval shorter than 50 microseconds. In the case where the device according to one of the above aspects of the present invention using the fuel pressure sensor is applied to a presently adopted general common rail system, the construction of sequentially obtaining the sensor output at the interval shorter than 50 microseconds is specifically effective to appropriately grasp the tendency of the pressure fluctuation mentioned above. However, in order to obtain the above-described pressure fluctuation mode with higher accuracy, a construction of sequentially obtaining the sensor output at a shorter interval is more desirable. Therefore, usually, it is desirable to set the interval for obtaining the sensor output (fuel pressure signal) to as short an interval as possible in consideration of disadvantage due to the increase in the time number of obtaining the sensor output or disadvantage due to increase in a computation load, for example.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of an embodiment will be appreciated, as well as methods of operation and the function of the related parts, from a study of the following detailed description, the appended claims, and the drawings, all of which form a part of this application. In the drawings:

FIG. 1 is a schematic diagram showing a system including a fuel injection control device according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view showing an internal structure of an injector used in the system according to the embodiment;

FIG. 3 is a side view showing an internal structure of a cylinder of a diesel engine according to the embodiment

FIG. 4 is a flowchart showing a basic procedure of fuel injection control processing according to the embodiment;

FIG. 5 is a flowchart showing a series of processing concerning data acquisition (learning processing) and differential value calculation according to the embodiment;

FIG. 6 is a time chart showing a setting mode of an execution period of the learning processing according to the embodiment;

FIG. 7 is a time chart showing a setting mode of an execution period of the learning processing according to the embodiment;

FIG. 8 is a time chart showing transitions of injection parameters according to the embodiment;

FIG. 9 is a time chart showing transitions of injection parameters according to the embodiment;

FIG. 10 is a flowchart showing a series of processing concerning detection of injection start timing according to the embodiment;

FIGS. 11A to 11C are maps used for variably setting a threshold value used for detecting the injection start timing according to the embodiment;

FIG. 12 is a flowchart showing a series of processing concerning detection of maximum injection rate reaching timing according to the embodiment;

FIG. 13 is a flowchart showing a series of processing concerning detection of injection end timing according to the embodiment;

FIG. 14 is a flowchart showing a series of processing concerning detection of timing at which the injection rate starts decreasing after reaching the maximum injection rate according to the embodiment;

FIGS. 15A and 15B are maps used for variably setting a return time used for detecting the injection rate decrease start timing according to the embodiment;

FIG. 16 is a flowchart showing an updating procedure of a correction coefficient of an injection command signal according to the embodiment;

FIGS. 17A and 17B are time charts showing an updating mode of the correction coefficient according to the embodiment;

FIG. 18 is a map used for calculation of ignition timing according to the embodiment;

FIG. 19 is a flowchart showing another updating mode of the correction coefficient of the injection command signal according to the embodiment;

FIG. 20 is a time chart showing a pressure varying mode according to the embodiment;

FIG. 21 is a cross-sectional view showing an internal structure of a direct acting piezo injector according to the embodiment.

FIGS. 22A to 22D are diagrams each showing a modification example of a basic diagram according to the embodiment; and

FIGS. 23A and 23B are diagrams each showing a modification example of the basic diagram according to the embodiment.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT

Hereafter, a fuel injection control device according to an embodiment of the present invention will be described with reference to the drawings. The control device according to the present embodiment is mounted, for example, in a common rail fuel injection system (high-pressure injection fuel supply system) for a diesel engine. That is, like the device described in Patent document 1, the control device according to the present embodiment is used for performing injection supply (direct injection supply) of high-pressure fuel (for example, light oil at injection pressure of 1000 atmospheres or higher) directly into a combustion chamber in a cylinder of a diesel engine.

First, an outline of the common rail fuel injection control system (an in-vehicle engine system) according to the present embodiment will be explained with reference to FIG. 1. It is assumed that the engine according to the present embodiment is a multi-cylinder engine (for example, an in-line four-cylinder engine) for a four-wheeled vehicle. In more detail, it is assumed that the engine according to the present embodiment is a four-stroke reciprocating diesel engine (internal combustion engine). In the engine, the cylinder as a target cylinder at the time is sequentially distinguished by a cylinder determination sensor (an electromagnetic pickup) provided to a camshaft of a suction valve or an exhaust valve. In each of the four cylinders #1-#4, a combustion cycle consisting of four strokes of an intake stroke, a compression stroke, a combustion stroke, and an exhaustion stroke is sequentially performed in an order of the cylinders #1, #3, #4, and #2 in a cycle of 720° CA, for example in more detail, while the combustion cycles are deviated from each other by 180° CA between the cylinders. The injectors 20 shown in FIG. 1 are injectors for the cylinders #1, #2, #3, and #4 from a fuel tank 10 side in this order.

As shown in FIG. 1, generally, the system is structured such that an ECU 30 (electronic control unit) takes in sensor outputs (sensing results) from various sensors and controls drive of respective devices constituting a fuel supply system based on the respective sensor outputs. The ECU 30 adjusts a supply quantity of current to a suction control valve 11 c, thereby controlling a fuel discharge quantity of a fuel pump 11 to a desired value. Thus, the ECU 30 performs feedback control (for example, PID control) for conforming fuel pressure in a common rail 12 (current fuel pressure sensed with a fuel pressure sensor 20 a) to a target value (target fuel pressure). The ECU 30 controls a fuel injection quantity to a predetermined cylinder of the target engine and an eventual output (i.e., rotation speed or torque of an output shaft) of the target engine to desired magnitudes based on the fuel pressure.

The devices constituting the fuel supply system including the fuel tank 10, the fuel pump 11, the common rail 12 (accumulator), and the injectors 20 are connected by predetermined pipes and are located in this order from a fuel upstream side. Among the devices, the fuel tank 10 and the fuel pump 11 are connected by a pipe 10 a via a fuel filter 10 b.

In such the fuel supply system, the fuel tank 10 is a tank (a vessel) for storing the fuel (light oil) of the target engine. The fuel pump 11 consists of a high-pressure pump 11 a and a low-pressure pump 11 b and is structured such that fuel drawn by the low-pressure pump 11 b from the fuel tank 10 is pressurized and discharged by the high-pressure pump 11 a. A fuel pumping quantity sent to the high-pressure pump 11 a and the eventual fuel discharge quantity of the fuel pump 11 are metered by the suction control valve 11 c (SCV) provided on a fuel suction side of the fuel pump 11. The fuel pump 11 can control the fuel discharge quantity from the pump 11 to a desired value by regulating drive current (eventually, a valve opening degree) of the suction control valve 11 c. For example, the suction control valve 11 c is a normally-on type metering valve that opens when de-energized.

The low-pressure pump 11 b out of the two kinds of pumps constituting the fuel pump 11 is constituted as a trochoid feed pump, for example. The high-pressure pump 11 a consists of a plunger pump, for example. The high-pressure pump 11 a is structured to be able to sequentially pump the fuel, which is sent to pressurization chambers, at predetermined timing by reciprocating predetermined plungers (for example, three plungers) in axial directions thereof with an eccentric cam (not illustrated) respectively. Both pumps 11 a, 11 b are driven by a drive shaft 11 d. The drive shaft 11 d is interlocked with a crankshaft 41 as an output shaft of the target engine and rotates at a ratio of 1/1, 1/2 or the like to one revolution of the crankshaft 41. That is, the low-pressure pump 11 b and the high-pressure pump 11 a are driven by an output of the target engine.

The fuel drawn by the fuel pump 11 from the fuel tank 10 through the fuel filter 10 b is pressure-fed (pumped) to the common rail 12. The common rail 12 accumulates the fuel pumped from the fuel pump 11 in a high-pressure state. The fuel accumulated in the high-pressure state in the common rail 12 is supplied to the injectors 20 of the respective cylinders #1-#4 through pipes 14 (high-pressure fuel passages) provided to the respective cylinders. An orifice (a restricting section of the pipe 14 as a fuel pulsation reducing device) is provided in a connection section 12 a between the common rail 12 and the pipe 14 (a common rail fuel discharge pipe). The orifice reduces a fuel pulsation transmitted to the common rail 12 through the pipe 14. The fuel pulsation is generated mainly in a fuel injection hole of the injector 20 during the injection. Thus, pressure pulsation in the common rail 12 can be reduced and the fuel can be supplied to each injector 20 at stable pressure. Fuel discharge holes of the injectors 20(#1)-20(#4) are connected with a pipe 18 for returning excess fuel to the fuel tank 10.

A detailed structure of the injector 20 is shown in FIG. 2. Basically, the four injectors 20(#1)-20(#4) have the same structure (for example, a structure shown in FIG. 2). Each injector 20 is a hydraulic drive type injector using the engine fuel to be combusted (i.e., the fuel in the fuel tank 10). In the injector 20, a driving power for the fuel injection is transmitted through an oil pressure chamber Cd (i.e., a command chamber).

As shown in FIG. 2, the injector 20 is a fuel injection valve of an inward-opening valve type. The injector 20 is structured as a fuel injection valve of a normally-closed type that is brought to a valve-closed state when de-energized. The high-pressure fuel is sent to the injector 20 from the common rail 12. In the present embodiment, the fuel pressure sensor 20 a (also refer to FIG. 1) is provided to a fuel inlet of the injector 20. Thus, fuel pressure (inlet pressure) at the fuel inlet can be sensed at any time. In more detail, a fuel pressure fluctuation (such as a pulsation pattern) accompanying actual injection or an injection operation of the injector 20, a static fuel pressure level during a non-injection period (i.e., stable pressure) and the like can be sensed (measured) with the output of the fuel pressure sensor 20 a.

When the injector 20 performs the fuel injection, an outer valve 202 b (a fluid control valve) opens/closes an orifice of1 (a restrictor) in accordance with an energization state (energization/de-energization) of a solenoid 201 b constituting a two-way electromagnetic valve 20 b. Thus, a sealed degree of the oil pressure chamber Cd and eventually pressure in the oil pressure chamber Cd (equivalent to back pressure of a needle 20 c) are increased/decreased. Due to the increase/decrease in the pressure, the needle 20 c reciprocates (moves upward and downward) inside a valve cylinder (i.e., inside a housing 20 e) along with or against an extensional force of a spring 20 d (a coil spring). Accordingly, a fuel supply passage to injection holes 20 f (necessary number of which are bored) is opened/closed in a middle thereof, or in more detail, at a tapered seat face, which the needle 20 c is seated on and which the needle 20 c is separated from in accordance with the reciprocating movement thereof.

Drive control of the needle 20 c is performed through PWM (Pulse Width Modulation) control. A pulse signal (an energization signal) is sent from the ECU 30 to the drive section (the two-way electromagnetic valve 20 b) of the needle 20 c. A lift amount of the needle 20 c (a separating degree from the seat face) is variably controlled based on the pulse width (equivalent to an energization period). In the control, basically, the lift amount increases as the energization period lengthens, and an injection rate (i.e., a fuel quantity injected per unit time) increases as the lift amount increases. The pressure increase processing of the oil pressure chamber Cd is performed by the fuel supply from the common rail 12. Pressure reduction processing of the oil pressure chamber Cd is performed by returning the fuel in the oil pressure chamber Cd to the fuel tank 10 through the pipe 18 (shown in FIG. 1) connecting the injector 20 and the fuel tank 10.

Thus, the injector 20 has the needle 20 c that performs valve opening and valve closing of the injector 20 by opening and closing the fuel supply passage extending to the injection holes 20 f through the predetermined reciprocating operation thereof inside the valve body (i.e., the housing 20 e). In a non-driven state, the needle 20 c is displaced in a valve-closing direction by the force (the extensional force of the spring 20 d) constantly applied to the needle 20 c in the valve-closing direction. In a driven state, the needle 20 c is applied with a driving force, so the needle 20 c is displaced in a valve-opening direction against the extensional force of the spring 20 d. The lift amount of the needle 20 c changes substantially symmetrically between the non-driven state and the driven state.

In the present embodiment, the fuel pressure sensors 20 a are provided to the neighborhoods of the respective injectors 20(#1)-20(#4), specifically, to the fuel inlets of the respective injectors 20(#1)-20(#4). A fluctuation mode of the fuel pressure accompanying the actual injection or the injection operation of the injector 20 concerning a predetermined injection can be sensed with high accuracy based on the outputs of the fuel pressure sensors 20 a (as mentioned in more detail later).

FIG. 3 is a side view schematically showing an internal structure of one of the four cylinders #1-#4 of the diesel engine as the target of the fuel supply of the present system. The structures of the four cylinders #1-#4 are fundamentally the same. Therefore, an explanation about the internal structure of each cylinder will be given here, paying attention to one cylinder 50 (for example, the cylinder #1).

As shown in FIG. 3, the cylinder 50 accommodates a piston 51 therein. The crankshaft 41 as the output shaft that is common to the respective cylinders #1-#4 and that has a flywheel is provided to the piston 51. The crankshaft 41 rotates in conjunction with reciprocating motion of the piston 51. In the cylinder, a combustion chamber Cm is formed between a top face of the piston 51 and a cylinder head. The injector 20 is provided in the combustion chamber Cm. A cylinder pressure sensor 53 is provided in the combustion chamber Cm, for example, integrally with a glow plug (not shown) as an ignition auxiliary equipment. The cylinder pressure sensor 53 measures pressure in the cylinder 50 (i.e., cylinder pressure) with a sensing portion (tip end portion of a probe inserted into the combustion chamber Cm) located in the combustion chamber Cm and outputs a sensing signal (an electrical signal) corresponding to a measurement value. An intake port and an exhaust port are provided in a portion of the cylinder head such that the intake port connects the combustion chamber Cm with an intake pipe and such that the exhaust port connects the combustion chamber Cm with an exhaust pipe. An intake valve 52 a and an exhaust valve 52 b are provided to the intake port and the exhaust port respectively. In the cylinder 50, each of the intake valve 52 a and the exhaust valve 52 b is driven by a cam that rotates in conjunction with the crankshaft 41. The cam is attached to a camshaft that rotates once in a period in which the crankshaft 41 rotates twice. Thus, each of the intake valve 52 a and the exhaust valve 52 b reciprocates at predetermined timing. Accordingly, the intake port and the exhaust port are opened and closed respectively by the valves.

Each cylinder of the target engine has such the structure. During an operation of the engine, an intake air is introduced into the combustion chamber Cm of the cylinder 50 from the intake pipe by an opening operation of the intake valve 52 a. The intake air is mixed with the fuel injected and supplied directly from the injector 20 (through direct injection supply) while the intake air is compressed by the piston 51 in the cylinder 50. The mixture gas of the intake air and the fuel ignites (through self ignition) and combusts. An exhaust gas produced through the combustion is discharged to the exhaust pipe by an opening operation of the exhaust valve 52 b. Thus, by causing the pistons of the cylinders to reciprocate in turn with the combustion of the fuel in the combustion chambers Cm, the crankshaft 41 as the output shaft rotates in conjunction with the reciprocation of the pistons 51.

In addition to the above-described sensors, various types of sensors for vehicle control are provided in a vehicle (not shown) such as a four-wheel passenger car or a truck. For example, a crank angle sensor 42 (for example, an electromagnetic pickup) that outputs a crank angle signal at every crank angle (for example, in the cycle of 30° CA) is provided to an outer periphery of the crankshaft 41 as the output shaft of the target engine to sense a rotational angle position of the crankshaft 41, rotation speed of the crankshaft 41 (i.e., engine rotation speed), and the like. An accelerator sensor 44 that outputs an electrical signal corresponding to a state (i.e., a displacement amount) of an accelerator is provided to the accelerator (i.e., an operation section) to sense an operation amount ACCP (i.e., a pressed amount) of the accelerator by the driver.

In such the system, it is the ECU 30 that functions as a fuel injection control device according to the present embodiment and that mainly performs the engine control as an electronic control unit. The ECU 30 (engine control ECU) has a well-known microcomputer (not shown). The ECU 30 grasps an operation state of the target engine and requests from the user based on the sensing signals of the above-described various types of sensors and operates the various types of actuators such as the suction control valve 11 c and the injectors 20 in accordance with the engine operation state and the requests of the user. Thus, the ECU 30 performs various kinds of control concerning the engine in the optimum modes corresponding to the situation of each time.

Fundamentally, the microcomputer mounted in the ECU 30 consists of various kinds of computing units, storage devices, signal processing devices, communication devices, power supply circuits and the like such as a CPU (basic processing unit) for performing various kinds of computation, a RAM (random access memory) as a main memory for temporarily storing data in the progress of the computation, results of the computation and the like, a ROM (read-only memory) as a program memory, an EEPROM (electrically rewritable nonvolatile memory) as a memory for data storage, a backup RAM (a memory invariably supplied with power from a backup power supply such as an in-vehicle battery even after a main power supply of the ECU 30 is stopped), signal processing devices such as an A/D converter and a clock generation circuit, and input/output ports for inputting/outputting the signals from/to an exterior. Various kinds of programs, control maps and the like concerning the engine control including programs concerning injection characteristic sensing and injection command correction are beforehand stored in the ROM. Various kinds of control data including design data of the target engine are beforehand stored in the memory for data storage (for example, the EEPROM).

In the present embodiment, the ECU 30 calculates torque (request torque) that should be generated in the output shaft (the crankshaft 41) at the time and eventually a fuel injection quantity for satisfying the request torque based on the various kinds of the sequentially inputted sensor outputs (sensing signals). Thus, the ECU 30 variably sets the fuel injection quantity of the injector 20 to control indicated torque (generation torque) generated through the fuel combustion in each cylinder (the combustion chamber) and eventual shaft torque (output torque) actually outputted to the output shaft (the crankshaft 41) (that is, the ECU 30 conforms the shaft torque to the request torque). That is, for example, the ECU 30 calculates the fuel injection quantity corresponding to the engine operation state, the operation amount of the accelerator by the driver and the like at each time and outputs an injection control signal (a drive amount) to the injector 20 for directing the fuel injection with the calculated fuel injection quantity in synchronization with desired fuel injection timing. Thus, i.e., based on the drive amount of the injector 20 (for example, a valve opening period), the output torque of the target engine is controlled to a target value.

As is well known, in the diesel engine, an intake throttle valve (a throttle) provided in an intake passage of the engine is held at a substantially fully-opened state during a steady operation for the purpose of increase in a fresh air quantity, reduction in a pumping loss and the like. Therefore, control of the fuel injection quantity is a main part of the combustion control during the steady operation (specifically, the combustion control concerning torque adjustment). Hereafter a fundamental procedure of the fuel injection control according to the present embodiment will be explained with reference to FIG. 4. Values of various parameters used in the processing shown in FIG. 4 are sequentially stored in the storage device mounted in the ECU 30 such as the RAM, the EEPROM or the backup RAM and are updated at any time when necessary. Fundamentally, a series of processing shown in FIG. 4 is serially performed at a frequency of one time per combustion cycle for each cylinder of the target engine through execution of the program stored in the ROM by the ECU 30. That is, with the program, fuel supply to all the cylinders except a dormant cylinder is performed during one combustion cycle.

As shown in FIG. 4, first in S11 (S means “Step”) in a series of the processing, predetermined parameters such as the engine rotation speed (i.e., an actual measurement value measured by the crank angle sensor 42) and the fuel pressure (i.e., an actual measurement value measured by the fuel pressure sensor 20 a) at the time are read and also the accelerator operation amount ACCP (i.e., an actual measurement value measured by the accelerator sensor 44) by the driver at the time and the like are read. Then, in following S12, an injection pattern is set based on the various parameters read in S11 (and also by separately calculating the request torque including losses due to external loads and the like when necessary).

The injection pattern is obtained based on a predetermined reference map (an injection control map or a mathematical expression) and a correction coefficient stored in the ROM, for example. In more detail, the optimum injection pattern (an adaptation value) is beforehand obtained by experiments and the like in anticipated ranges of the predetermined parameters (read in S11) and is written in the map, for example. For example, the injection pattern is defined by parameters such as the number of injection stages (i.e., the time number of injections performed in one combustion cycle), injection timing of each injection (i.e., injection timing) and an injection period (equivalent to an injection quantity) of each injection. Moreover, in the present embodiment, a reference diagram indicating a diagram to be created as a profile of a transition of an injection rate is also included in the parameters of the injection pattern. The reference diagram serves as a parameter that shows characteristics of each injection. In the present embodiment, a diagram (e.g., a trapezoid or a triangle) defined by an area and injection start timing is adopted as the reference diagram, for example. The area of the reference diagram corresponds to the fuel injection quantity (the injection quantity concerning the injection). For example, in the case of a single injection, the area of the diagram (i.e., the fuel injection quantity) of the injection is variably set in accordance with the torque that should be generated in the output shaft (the crankshaft 41) (i.e., the request torque equivalent to an engine load at the time). In the case of an injection pattern of multistage injection (multi-injection), the summation of the areas of the diagrams (i.e., a total injection quantity) of injections contributing to the torque is variably set in accordance with the torque that should be generated in the output shaft (the crankshaft 41).

The above-described map indicates the relationship between the parameters and the optimum injection pattern. The injection pattern obtained based on the map is corrected with a correction coefficient (stored in the EEPROM in the ECU 30, for example) that is separately updated (in a manner explained in more detail later). For example, a set value is calculated by dividing the map value by the correction coefficient. Thus, the injection pattern of the injection to be performed at the time is obtained. When the injection pattern is set (in S12), maps set individually for the respective elements of the injection pattern (such as the number of the injection stages) may be used. Alternatively, maps, each of which is made for some collective elements of the injection pattern, or a map for all the elements of the injection pattern may be used.

In following S13, a command signal for the injector 20 is produced based on the injection pattern set in this way. A command value corresponding to the thus produced injection pattern is used in following S14. That is, in S14, the drive of the injector 20 is controlled based on the command value (the command signal), or in more detail, by outputting the command signal to the injector 20. Thus, a pilot injection, a pre-injection, an after injection, a post-injection and the like are suitably performed with a main injection in accordance with the situation of the vehicle and the like. After the drive control of the injector 20, the series of the processing shown in FIG. 4 is ended.

In the present embodiment, the diagram (including parameters of the diagram) as the profile of the transition of the injection rate of the target injector 20 at the time is detected based on the output of the fuel pressure sensor 20 a. Then, based on the detected diagram and the basic diagram (S12 of FIG. 4) mentioned above, the injection command to the injector 20 is varied such that the diagram as the actual profile of the transition of the injection rate becomes a diagram belonging to the basic diagram and such that a relative positional relationship between an injection centroid of the diagram as the actual profile of the injection rate transition and an injection centroid of the basic diagram becomes a predetermined relationship (i.e., such that timings of the both injection centroids approximate to each other). More specifically, a correction coefficient for the reference map (S12 of FIG. 4), in which the injection command used when performing the injection control with the injector 20 is written, is sequentially updated. More specifically, coefficients concerning the above-described basic diagram out of the multiple kinds of coefficients are sequentially updated. Thus, the injection command to the injector 20 is varied.

Next, a mode of detecting each timing concerning the above-described fuel injection (i.e., the injection timing) based on the output of the fuel pressure sensor 20 a will be explained in detail with reference to FIGS. 5 to 15B.

In the detection of the injection timing, the output of the fuel pressure sensor 20 a is taken in first, and then, a first order differential value dP and a second order differential value ddP of the fuel pressure P at each timing are calculated from the output. FIG. 5 is a flowchart showing a series of processing concerning the data acquisition (obtainment and storage of the sensor output: learning processing) and differential value calculation. Fundamentally, a series of processing shown in FIG. 5 is serially performed at a predetermined processing interval (e.g., at an interval of 20 μsec) through execution of a program stored in the ROM by the ECU 30. Values of various parameters used in the processing shown in FIG. 5 are serially stored in the storage device mounted in the ECU 30 such as the RAM, the EEPROM or the backup RAM and are updated at any time when necessary.

As shown in FIG. 5, in a series of the processing, the output of the fuel pressure sensor 20 a is taken in first in S21. In following S22, a pressure first order differential value dP is calculated as a difference between a present value and a previous value of the pressure value P (i.e., dP=P(present)−P(previous)). In following S23, a pressure second order differential value ddP is calculated as a difference between a present value and a previous value of the pressure first order differential value dP (i.e., ddP=dP(present)−dP(previous)). Then in following S24, the respective data P, dP, ddP are stored and the series of the processing is ended.

Next, an execution period and a setting mode of the processing shown in FIG. 5 will be explained with reference to FIGS. 6 and 7, In FIG. 6 or 7, part (a) is a time chart showing a transition of the injection command signal INJ (the pulse signal) to the injector 20, part (b) is a time chart showing a transition of the injection rate R (i.e., the fuel quantity injected per unit time), and (c) is a time chart showing a transition of the fuel pressure P (i.e., the inlet pressure) sensed with the above-described fuel pressure sensor 20 a (shown in FIG. 1).

As shown in FIG. 6, in the present embodiment, multiple injections (for example, three-stage injections of a pilot injection Prt, a main injection Mn and a post-injection Pst shown in FIG. 6) are performed by the injector 20 during a combustion cycle of the engine in some cases. When a sensor output acquisition period is set, start timing of the sensor output acquisition period (i.e., a sensing period: a period indicated by “SENSING” in FIG. 6) is set to injection start command timing (timing t101) of the injector 20, which is directed by an injection start command concerning the earliest injection in the combustion cycle (for example, the pilot injection Prt shown in FIG. 6). The energization is started at the injection start command timing t101 of the injector 20. Furthermore, end timing (timing t102) of the above-described sensing period is set based on a pressure fluctuation mode after execution of the latest injection in the same combustion cycle (for example, the post-injection Pst shown in FIG. 6). In more detail, the end timing (timing t102) of the sensing period is set to timing (equivalent to injection end timing) when the pressure fluctuation caused by the post-injection Pst converges. Thus, the above-described sensing period is set at least to the period from the start of the pressure fluctuation due to the pilot injection Prt to the end of the pressure fluctuation due to the post-injection Pst in a limited way. That is, the sensing period is set to a predetermined period (from the timing t101 to the timing t102) including a period (a pressure fluctuation period), in which the pressure fluctuation is caused by the actual injection of the injector 20, in a limited way.

Fundamentally, desired data (a waveform of the pressure fluctuation related to the injection) can be obtained even during such the limited period. It is because the period excluded by the limitation of the sensing period is a period that is not a sensing target, i.e., a period in which only unnecessary data can be obtained (sensed) normally. Since the sensing period is set as the short and limited period, a processing load of the ECU 30 can be reduced and a used storage area of the RAM can be reduced.

Moreover, in the present embodiment, a period (a stoppage period from t101 a to t102 a indicated by “STOP” in FIG. 7) for temporarily suspending the acquisition of the sensor output is set at least in a part of a period (a pressure stabilization period) in which the fuel pressure at the installation position of the fuel pressure sensor 20 a is stable in the period (the sensing period) set in the above-mentioned mode for sequentially acquiring the output of the fuel pressure sensor 20 a as shown in FIG. 7. In more detail, if a lift amount of the needle 20 c of the injector 20 (shown in FIG. 2) becomes sufficiently large to the extent that sufficient high-pressure fuel is supplied to the injection holes 20 f (shown in FIG. 2), the injection rate R converges to a substantially constant value at an injection limit defined by a bore diameter of the injection hole 20 f (i.e., a fuel outlet area). Therefore, in such the period, with the stabilization of the injection rate R, the pressure P sensed with the fuel pressure sensor 20 a, i.e., the fuel pressure in the fuel passage where the sensor 20 a is installed, is also stabilized. In the present embodiment, start timing (timing t101 a) of such the pressure stabilization period is sensed based on the sensor output (a pressure fluctuation mode) of the sensor 20 a at each time. The start timing of the stoppage period is set at the start timing t101 a of the sensed pressure stabilization period. More strictly, the start timing of the stoppage period is set at timing when the start timing of the pressure stabilization period is decided. Furthermore, end timing of the stoppage period is set at injection end command timing (i.e., the timing t102 a) directed by the injection end command to the injector 20.

Thus, in the present embodiment, the above-described sensing period is further limited by providing the stoppage period t101 a-t102 a. Fundamentally, desired data (a waveform of the pressure fluctuation related to the injection) can be obtained even during such the limited sensing periods t101-t101 a, t102 a-t102. It is because the period excluded by the above-described limitation of the sensing period is a period in which the fuel pressure P is stable and the fuel pressure P in such the excluded period can be fundamentally estimated by interpolation calculation and the like based on the pressure values before and after the stoppage period t101 a-t102 a. Since the sensing period is set as the further short and limited period, a processing load of the ECU 30 can be reduced further and a used storage area of the RAM can be reduced further.

FIG. 8 is a time chart showing an example of the pressure transition waveform obtained in S21 of FIG. 5. In FIG. 8, a solid line PL10 in part (a) indicates a transition of the injection command signal INJ (the pulse signal) to the injector 20, a solid line R10 in part (b) indicates a transition of the injection rate R (the fuel quantity injected per unit time), and a solid line P10 in part (c) indicates a transition of the fuel pressure P (the inlet pressure) sensed with the above-described fuel pressure sensor 20 a. FIRST in FIG. 8 indicates a first stage injection and SECOND is a second stage injection.

As shown in FIG. 8, the sensor output acquired in S21 of FIG. 5 contains a high-frequency noise. In the present embodiment, filtering processing is applied to the sensor output by letting the sensor output pass through a low-pass filter (or a band pass filter). Then, in following S22 and S23, first order differential processing and second order differential processing are applied to the filtered data (the data from which the high-frequency noise is removed). Thus, the above-mentioned differential data are derived (calculated). Thus, the change in the fuel pressure P accompanying the change in the actual injection state or the injection operation state can be sensed with high accuracy.

FIG. 9 is a time chart showing an example of pressure transition waveforms acquired and stored (i.e., learned) through the processing shown in FIG. 5. In FIG. 9, part (a) is a time chart showing a transition of the injection rate R (i.e., the fuel quantity injected per unit time), part (b) is a time chart showing waveform data after the above-described filtering processing is applied to the sensor output, part (c) is a time chart showing waveform data after the first order differential processing is applied to the data having undergone the filtering processing, and part (d) is a time chart showing waveform data after the second order differential processing is applied to the data having undergone the filtering processing. In FIG. 9, chained lines show data of a fuel pressure level (fuel pressure immediately before injection) of 75 MPa, solid lines show data of a fuel pressure level of 80 MPa, and chain double-dashed lines show data of a fuel pressure level of 85 MPa, respectively.

As shown in part (b) of FIG. 9, the pressure transition after rising timing of the injection command pulse to the injector 20 (i.e., the energization start timing) (equivalent to timing before timing t0) indicates a following tendency as a general tendency. That is, there is a short period in which the pressure P is constant first, and after the period, the pressure P starts to gradually decrease at the timing t0 shown in FIG. 9. Then, the pressure P starts to decrease steeply at timing t1. The initial period in which the pressure P is constant and the following period t0-t1 in which the pressure P gradually decreases correspond to an invalid injection time (an invalid injection period) of the injector 20. In more detail, the invalid injection time is a summation of various kinds of delays such as a delay since the energization (rising of the injection command pulse) occurs until a normal magnetic field is formed by the solenoid 201 b (shown in FIG. 2) and an operation delay due to an inertia of the outer valve 202 b, the needle 20 c and the like (shown in FIG. 2), an inertia of the fuel, a friction with a wall surface inside the nozzle, and the like. The invalid injection time is equivalent to a time since the drive (the energization) of the injector 20 is started until the fuel is actually injected.

The pressure P decreases gradually in a period after the period of the constant pressure P in the invalid injection period. This shows that pressure leak is caused by the injection operation of the injector 20. More specifically, this phenomenon occurs because the injector 20 is an injector of a type that is accompanied by pressure leak during a period since the injector starts an operation concerning the injection (i.e., an opening operation of the outer valve 202 b) until the injection is actually started. More specifically, as mentioned above, the injector 20 returns the fuel in the oil pressure chamber Cd to the fuel tank 10 by opening the orifice of1 to drive the needle 20 c when the injector 20 is energized (ON). Therefore, the fuel pressure due to the common rail 12 leaks through the orifice of1 (shown in FIG. 2) during the injection operation of the injector 20. That is, the pressure drop at the time (i.e., the pressure drop in the period from to t1) corresponds to the gentle decrease of the pressure P (i.e., the pressure leak) in the above-described invalid injection period.

As contrasted thereto, a pressure drop point (i.e., the timing t0) when the pressure P starts to fall steeply corresponds to the timing when the injection is actually started through the injector 20 (i.e., the injection start timing).

As shown in FIG. 9, the pressure transition (the pressure transition waveform) after the above-described injection start timing (the timing t1) has a following tendency as a general tendency. That is, a transition is made from the steep pressure drop at the timing t1 to a pressure local minimum point at timing t2 and a stable period of the pressure value at the pressure minimum point, and then, a transition is made to pressure increase at timing t2 a. After that, the pressure P is stabilized once at timing t2 b but rises steeply at timing t3 again. If the pressure P eventually reaches a level near a pressure value before the injection (i.e., a zero crossing point) at timing t4, the pressure P surges (pulsates) near the pressure value.

The timing t2 corresponds to timing when the injection rate R is maximized (hereinafter, referred to as a maximum injection rate reaching timing).

The timing t2 a corresponds to timing when the outer valve 202 b closes. The timing t3 corresponds to timing when the injection rate R starts to decrease after reaching the maximum injection rate (hereinafter, referred to as injection rate decrease start timing). The timing t4 corresponds to timing when the injection by the injector 20 stops, i.e., the injection end timing. Like the invalid injection time in the injection start, there occurs a delay from the de-energization (i.e., falling of the injection command pulse) to the injection end timing (the timing t4) also in the injection end of the injector 20.

Next, processing for detecting the respective timings (timings t1-t4) concerning the above-described fuel injection will be explained in detail with reference to FIGS. 9 to 15B based on the pressure transition waveforms shown in parts (b) to (d) of FIG. 97 i.e., the pressure transition waveforms acquired and stored (i.e., learned) thought the processing of FIG. 5. FIGS. 10 and 12 to 14 are flowcharts showing a series of processing concerning the detection of the respective timings. Fundamentally, a series of processing shown in the drawings is serially performed at a predetermined interval (e.g., at an interval of 20 μsec) through execution of programs stored in the ROM by the ECU 30. Through the execution of the processing, the detection and the storage of the above-described timings are performed once per injection. That is, in the case of a single-stage injection, a set of the detection and storage is performed once per combustion cycle. In the case of a two-stage injection, two sets of the detection and storage are performed per combustion cycle. Values of various parameters used in the processing shown in the respective drawings are serially stored in the storage device mounted in the ECU 30 such as the RAM, the EEPROM or the backup RAM and are updated at any time when necessary like the processing shown in FIG. 5.

Processing shown in FIG. 10 is for detecting the above-described injection start timing (the timing t1).

As shown in FIG. 10, in a series of the processing, first in S31, it is determined whether the injection start command (the energization start) of a certain injection has been made and the timing t1 has not been detected yet. Only when it is determined that the injection start command of the certain injection has been made and the timing t1 has not been detected yet in S31, processing from S32 is performed. That is, a period in which the condition of S31 is satisfied corresponds to a sensing period of the above-described timing t1.

In S32, it is determined whether the pressure second order differential value ddP calculated in S23 of FIG. 5 is smaller than a predetermined threshold value K1 (ddP<K1).

The threshold value K1 is set at a value smaller than 0 (K<0), i.e., at a negative value. When the value K1 is set, the value K1 is variably set based on multiple maps obtained through experiments and the like beforehand, e.g., maps shown in FIGS. 11A to 11C. This responds to the phenomenon that the inclination of the pressure drop (shown in FIG. 9) accompanying the above-mentioned injection start changes in accordance with the fuel pressure P immediately before the injection (i.e., the fuel pressure level at the time of the stability before the timing to of FIG. 9), the injection execution timing, the cylinder pressure and the like. That is, the threshold value K1 is set at a smaller value (i.e., at a larger value on the negative side) as the inclination of the pressure drop becomes steeper.

FIG. 11A is a map showing a relationship between the fuel pressure level P (i.e., the actual measurement value measured by the fuel pressure sensor 20 a) and an adaptation value (i.e., the optimum value) of the threshold value K1 obtained by experiment and the like. As shown in FIG. 11A, according to the map, the threshold value K1 is set at a smaller value as the fuel pressure level P increases before the fuel pressure level P reaches a convergence point (80 MPa, in this example). If the fuel pressure level P reaches the convergence point, a degree of the decrease in the threshold value K1 with respect to the increase in the fuel pressure level P becomes very small.

FIG. 11B is a map showing a relationship between the injection execution timing and the adaptation value (i.e., the optimum value) of the threshold value K1 obtained through experiment and the like. The injection execution timing is detected as the injection start command timing directed by the injection start command to the injector 20, or in more detail, as the rising timing of the injection command pulse (i.e., the energization start timing). As shown in FIG. 11B, according to the map, the threshold value K1 is set at a smaller value as the injection execution timing comes closer to TDC (a top dead center).

FIG. 11C is a map showing a relationship between the pressure inside the cylinder of the target engine (i.e., the actual measurement value measured by the cylinder pressure sensor 53 shown in FIG. 3) and the adaptation value (the optimum value) of the threshold value K1 obtained through experiment and the like. As shown in FIG. 11C, according to the map, the threshold value K1 is set at a smaller value as the cylinder pressure increases.

Thus, in the present embodiment, the threshold value K1 is variably set in accordance with the inclination of the pressure drop. Accordingly, the above-described pressure drop accompanying the injection and eventually the injection start timing (the timing t1 shown in FIG. 9) can be detected with high accuracy.

The processing of S32 is repeatedly performed in the sensing period of the timing t1. The series of the processing of FIG. 10 is ended if it is determined that the pressure second order differential value ddP is not smaller than the threshold value K1 in S32. If it is determined that the pressure second order differential value ddP is smaller than the threshold value K1, the present timing is stored as the injection start timing (the timing t0) in a predetermined storage device in following S33. The fuel pressure P at the timing t1 (corresponding to a reference point of the injection rate R (=0)) is also stored in the same storage device. In this case, it is effective to store the timing and the fuel pressure P in a predetermined storage device (for example, the EEPROM or the backup RAM) capable of holding the data even after the stoppage of the main power supply to the ECU 30, while relating the data to a predetermined parameter (for example, an engine state as of the data acquisition) if needed. Thus, the data is held in the storage device in a non-volatile manner without being erased even after the target engine is stopped and the power supply to the ECU 30 is blocked out. As a result, preservation of the data and eventually read-out of the data over a long period of time are enabled. If the data is related to the predetermined parameter when the data is stored, the data retrieval is facilitated by using the parameter when the data is read. Thus, data analysis and the like can be performed easily and appropriately.

Thus, in the present embodiment, the timing when the pressure drop accompanying the injection start occurs or eventually the injection start timing (the timing t1 of FIG. 9) is detected as the timing (a crossing point), at which the pressure second order differential value ddP shifts from the larger side than the threshold value K1 to the smaller side than the threshold value K1. With such the detection scheme, the above-described pressure drop can be grasped accurately, and eventually the injection start timing can be detected accurately.

Processing shown in FIG. 12 is for detecting the above-described maximum injection rate reaching timing (i.e., the timing t2).

As shown in FIG. 12, in a series of the processing, first in S41, it is determined whether the timing t1 of the aforementioned injection has been detected and the timing t2 of the injection has not been detected yet. Only when it is determined that the timing t1 of the injection has been detected and the timing t2 of the injection has not been detected yet in S41, processing from S42 is performed. That is, a period in which the condition of S41 is satisfied corresponds to a sensing period of the above-described timing t2.

In S42, it is determined whether the previous value of the pressure first order differential value dP calculated in S 22 of FIG. 5 is smaller than 0 (i.e., dP(previous)<0) and the present value of the pressure first order differential value dP is equal to or greater than a predetermined threshold value K2 (i.e., dP(present)≧K2). The threshold value K2 may be a fixed value or a variable value. The threshold value K2 is set at a value greater than 0, i.e., a positive value (k2>0).

The processing of S42 is repeatedly performed in the sensing period of the timing t2. If it is not determined in S42 that dP(previous)<0 and dP(present)≧K2, the series of the processing of FIG. 12 is ended. If it is determined in S42 that dP(previous)<0 and dP(present)≧K2, the present timing is stored as the maximum injection rate reaching timing (the timing t2 shown in FIG. 9) in a predetermined storage device (for example, the EEPROM, the backup RAM or the like) in following S43. The fuel pressure P at the timing t2 is also stored in the same storage device. A decrease amount of the fuel pressure P from the timing t1 corresponds to the injection rate R at the timing t2.

Thus, in the present embodiment, the timing when the fuel pressure P is stabilized after the end of the steep decrease of the fuel pressure P caused at the injection start or eventually the maximum injection rate reaching timing (the timing t2 shown in FIG. 9) is detected as the timing (a crossing point), at which the pressure first order differential value dP shifts from the smaller side than the threshold value K2 to the larger side than the threshold value K2. With such the detection scheme, the above-described timing when the fuel pressure P stabilizes can be grasped accurately and eventually the maximum injection rate reaching timing can be detected accurately.

Processing shown in FIG. 13 is for detecting the above-described injection end timing (timing t4).

As shown in FIG. 13, in a series of the processing, first in S51, it is determined whether the timing t2 of the aforementioned injection has been detected and the timing t4 of the injection has not been detected yet. Only when it is determined that the timing t2 of the injection has been detected and the timing t4 of the injection has not been detected yet in S51, processing from S52 is performed. That is, a period in which the condition of SS1 is satisfied corresponds to a sensing period of the above-described timing t4.

In S52, it is determined whether a previous value of the pressure first order differential value dP calculated in S22 of FIG. 5 is greater than 0 (dP(previous)>0) and a present value of the pressure first order differential value dP is equal to or smaller than a predetermined threshold value K3 (i.e., dP(present)≦K3). The threshold valve K3 may be a fixed value or a variable value. The threshold value K3 is set at a value smaller than 0, i.e., a negative value (K3<0).

The processing of S52 is repeatedly performed in the sensing period of the timing t4. If it is not determined in S52 that dP(previous)>0 and dP(present)≦K3, the series of the processing of FIG. 13 is ended. If it is determined in S52 that dP(previous)>0 and dP(present)≦K3, the present timing is stored as the injection end timing (the timing t4 shown in FIG. 9) in a predetermined storage device (for example, the EEPROM, the backup RAM or the like) in following S53. The fuel pressure P at the timing t4 is also stored in the same storage device.

Thus, in the present embodiment, the timing when the pulsation of the fuel pressure P starts after the end of the steep increase of the fuel pressure P due to the closing of the injector or eventually the injection end timing (the timing t4 shown in FIG. 9) is detected as the timing (a crossing point), at which the pressure first order differential value dP shifts from the larger side than the threshold value K3 to the smaller side than the threshold value K3. With such the detection scheme, the change in the above-described pressure fluctuation mode can be grasped accurately, and eventually the injection end timing can be detected accurately.

Processing shown in FIG. 14 is for detecting timing (the timing t3), at which the injection rate R starts to decrease after reaching the above-described maximum injection rate (at the timing t2).

As shown in FIG. 14, in a series of the processing, first in S61, it is determined whether the timing t4 of the aforementioned injection has been detected and the timing t3 of the injection has not been detected yet. Only when it is determined that the timing t4 of the injection has been detected and the timing t3 of the injection has not been detected yet in S61, processing from S62 is performed.

In S62, the timing (i.e. the timing t3 shown in FIG. 9), at which the injection rate R starts to decrease after reaching the maximum injection rate, is detected as timing earlier than the injection end timing (timing t4) by a predetermined return time Tc (t3=t4−Tc). In following S63, the timing t3 is stored in a predetermined storage device (for example, the EEPROM, the backup RAM or the like). The fuel pressure P (corresponding to the injection rate) at the timing t3 is also stored in the same storage device.

The return time Tc is variably set based on multiple maps obtained through experiments and the like beforehand, e.g., maps shown in FIGS. 15A and 15B. This responds to the phenomenon that the period since the injection rate R starts to decrease until the injection ends changes in accordance with the fuel pressure P immediately before the injection (i.e., the fuel pressure level at the time when the pressure is stable) and the injection period.

FIG. 15A is a map showing a relationship between the fuel pressure level P (i.e., the actual measurement value measured by the fuel pressure sensor 20 a) and an adaptation value (i.e., the optimum value) of the return time Tc obtained through the experiment and the like. As shown in FIG. 15A, according to the map, the return time Tc is set at a shorter time as the fuel pressure level P (i.e., base pressure) increases.

FIG. 15B is a map showing a relationship between the injection period (which is detected as pulse width TQ of the injection command, for example) and an adaptation value (i.e., the optimum value) of the return time TIc obtained through the experiment and the like. As shown in FIG. 15B, according to the map, the return time Tc is set at a longer time as the injection period lengthens.

Thus, in the present embodiment, the timing (the timing t3 shown in FIG. 9) at which the injection rate R starts decreasing after reaching the above-described maximum injection rate is detected based on a relative positional relationship between the timing t3 and the timing t4 detected through the processing shown in FIG. 13. With such the detection scheme, the timing t3 shown in FIG. 9 can be detected easily and accurately.

As described above, in the present embodiment, the injection start timing, the maximum injection rate reaching timing, the timing at which the injection rate R starts decreasing after reaching the maximum injection rate, and the injection end timing are sequentially detected for each injection (each of the multiple injections performed during a combustion cycle in the case of the multi-injection) respectively through the processing shown in FIGS. 5, 10, and 12 to 14 based on the output of the above-described fuel pressure sensor 20 a. Based on the timings, or more specifically, by producing a diagram by connecting the points of the respective timings, a diagram (a trapezoid or a triangle) as a profile of the injection rate transition of the target injector 20 at the time and parameters of the diagram (an area of the diagram, timings of corners of the diagram, an injection rate and the like) are sensed.

Then, correction coefficients for the reference map (used in S12 of FIG. 4) (more specifically, coefficients concerning the above-described basic diagram out of the multiple kinds of coefficients) are sequentially updated based on the detected diagram (the sensed diagram) and the above-mentioned basic diagram (used in S12 of FIG. 4) such that the diagram as the actual profile of the injection rate transition becomes a diagram belonging to the basic diagram and such that a relative positional relationship between an injection centroid of the diagram as the actual profile of the injection rate transition and an injection centroid of the basic diagram (i.e., geometric centroids of the diagrams) becomes a predetermined relationship (or in more detail, such that timings of the both injection centroids approximate to each other). That is, when the detected diagram is a diagram other than the basic diagram, the correction coefficients are updated in the subsequent combustion cycle such that the diagram as the profile of the injection rate transition becomes a diagram belonging to the basic diagram and such that timing of the injection centroid of the diagram approaches timing of the injection centroid of the basic diagram. Next, an updating mode of the correction coefficients according to the embodiment will be explained with reference to FIGS. 16 to 18. Hereafter, for the sake of convenience of the explanation, the explanation will be given by using a case where the basic diagram is a triangle (i.e., a delta shape, or a diagram equivalent to a trapezoid, in which a period t2-t3 (FIG. 9) is brought to zero) as an example.

FIG. 16 is a flowchart showing a series of processing concerning the updating processing of the correction coefficients. Fundamentally, a series of the processing shown in FIG. 16 is sequentially performed through execution of a program stored in the ROM by the ECU 30 every time the diagram as the profile of the injection rate transition of the target injection is detected. Values of various parameters used in the processing shown in FIG. 16 are sequentially stored in the storage device mounted in the ECU 30 such as the RAM, the EEPROM or the backup RAM and are updated at any time when necessary.

As shown in FIG. 16, first in S71 in the processing, the maximum injection rate of the basic diagram, i.e., a target value of the maximum injection rate (target Rmax), and the maximum injection rate of the detected diagram, i.e., a sensing value of the maximum injection rate (sensed Rmax), are detected and compared with each other. Thus, it is determined whether a deviation amount between the target value and the sensing value of the maximum injection rate Rmax is within a permissible level (for example, a deviation amount between the both values<predetermined determination value, e.g., sensed Rmax=target Rmax as shown in FIG. 16). When it is determined that the deviation amount of the maximum injection rate Rmax is greater than the permissible level in S71, it is determined that the timing of the injection centroid (geometric centroid) of the detected diagram is deviated from the timing of the injection centroid of the basic diagram and the processing proceeds to S72. When the basic diagram is the triangle the injection rate at the apex of the triangle corresponds to the maximum injection rate Rmax. In the case of the trapezoid, the injection rate at the timing t2 or the timing t3 or an injection rate calculated based on the both timings (for example, through averaging) may be used as the maximum injection rate Rmax.

In S72, the correction coefficients of the injection command to the injector 20 are updated to approximate the timing of the injection centroid of the diagram as the actual profile of the injection rate transition and the timing of the injection centroid of the basic diagram to each other. An adjustment mode of the injection centroid is shown in FIGS. 17A and 17B.

As shown in FIG. 17A, in this example, the basic diagram is a triangle L0 defined by an injection start point (timing t10), a maximum injection rate reaching point (the maximum injection rate LV10 equivalent to the target value of the maximum injection rate), and an injection end point (timing t40), and the detected diagram is a triangle L1 defined by an injection start point (timing t1), a maximum injection rate reaching point (the maximum injection rate LV1 equivalent to the sensing value of the maximum injection rate), and an injection end point (timing t4). Between the two diagrams, timing t50 of the injection centroid of the basic diagram and timing t5 of the injection centroid of the detected diagram are deviated from each other by a deviation amount Td.

In S72 of FIG. 16, the geometric centroids (the injection centroids) of the both diagrams are detected and the correction coefficients (equivalent to the injection command) are produced such that the timings of the injection centroids of the both diagrams coincide with each other. In the present embodiment, in order to change the timings t1, t4 of the detected diagram to timings t1 a, t4 a shown in FIG. 17B by advancing the timings t1, t4 of the detected diagram by the deviation amount Td respectively (at a ratio of 1.1 between the both timings), the correction coefficients for advancing rising timing and falling timing of the pulse signal by the deviation amount Td respectively with respect to an injection result (injection data) obtained in the present combustion cycle are produced and updated as values for the next combustion cycle.

Thus, the entire diagram is also adjusted with the adjustment of the injection start timing and the injection end timing. Also, the timing of the injection centroid moves by the same displacement amount as the displacement amount of each timing. Thus, in the present embodiment, the timing t50 of the injection centroid of the basic diagram and the timing t5 of the injection centroid of the detected diagram are approximated to each other by adjusting injection timings (i.e., the injection start timing and the injection end timing).

However, in this case, if the injection execution timing (i.e., the injection start timing) is changed without limitation, ignition timing will deviate largely from a reference value (i.e., a value originally anticipated), and as a result, there occurs a possibility of causing an unexpected situation (i.e., a phenomenon not checked by the experiment or the like). Therefore, in the present embodiment, a guard is defined to an adjustment range of the injection start timing (on at least one of an upper limit side and a lower limit side). For example, with reference to a certain map such as a map shown in FIG. 18 defining a tendency that an ignition delay shortens as the injection execution timing comes closer to a TDC, a time (i.e., an ignition delay) from the injection start to the ignition is calculated based on the injection execution timing at the time (i.e., the timing t1 described above) and the ignition timing of the injection is calculated based on the ignition delay (i.e., the ignition timing=timing t1+ignition delay). The guard is defined to the adjustment range of the injection start timing such that the ignition timing, i.e., the ignition timing in the present combustion cycle, falls within a predetermined permissible range. Thus, the timing t50 of the injection centroid of the basic diagram and the timing t5 of the injection centroid of the detected diagram can be approximated to each other while maintaining the ignition timing within the permissible range. As a result, reliable injection control can be realized.

Thus, in the present embodiment, the correction coefficients for the reference injection map (S12 of FIG. 4) are updated in the above-described mode for each injection (each of multiple injections in a combustion cycle in the case of the multi-injection) at each timing of the injection. Thus, the injection command to the injector 20 concerning each injection defined in the map is continuously updated, realizing appropriate injection control over a long period of time.

As explained above, the fuel injection control device according to the present embodiment exerts following outstanding effects.

(1) The fuel injection control device (the ECU 30 for engine control) according to the above-described embodiment is applied to the fuel supply system that performs the injection supply of the fuel into the cylinder as a portion performing the fuel combustion of the target engine with the predetermined injector (injector 20) and controls the injection supply of the fuel to the target engine. The fuel injection control device includes the program (a fuel pressure sensing section: S21 of FIG. 5) for sequentially sensing the fuel pressure fluctuating with the injection by the injector 20. The fuel injection control device includes the program (an injection centroid detecting section: S72 of FIG. 16) for detecting a geometric centroid of the diagram (i.e., the injection centroid) as the present profile of the fuel quantity injected from the injector 20 per unit time (i.e., the injection rate) based on the transition of the fuel pressure sequentially sensed by the above program (the fuel pressure sensing section). The fuel injection control device includes the program (an injection varying section) for varying the injection command (the injection timing) to the injector 20 based on the injection centroid detected by the above program (the injection centroid detecting section) and the injection centroid of the predetermined basic diagram such that the relative positional relationship between the injection centroid of the diagram as the actual profile of the injection rate transition and the injection centroid of the basic diagram becomes a predetermined relationship (i.e., such that the timings of the injection centroids approximate to each other). With such the construction, the injection command and eventually the position of the injection centroid are adjusted in accordance with the injection characteristic of each time, thereby enabling appropriate fuel injection control.

(2) In S72 of FIG. 16, the injection command to the injector 20 is varied to approximate the timing of the injection centroid of the diagram as the actual profile of the injection rate transition and the timing of the injection centroid of the basic diagram to each other. Thus, the injection characteristics (output torque, emission characteristics and the like of the target engine) are improved.

(3) In S72 of FIG. 16, the injection start timing and the injection end timing are adjusted to approximate the timing of the injection centroid of the diagram as the actual profile of the injection rate transition and the timing of the injection centroid of the basic diagram to each other. Thus, the timing of the injection centroid can be adjusted easily and appropriately.

(4) In S72 of FIG. 16, both the injection start timing and the injection end timing of the injector 20 are adjusted at a predetermined ratio of 1:1. Thus, the timing of the injection centroid can be adjusted easily.

(5) The entire diagram is adjusted while adjusting both of the injection start timing and the injection end timing at the ratio of 1:1. Thus, the timing of the injection centroid moves by the same displacement amount as the displacement amount of each timing. As a result, the timing of the injection centroid can be easily adjusted.

(6) In S72 of FIG. 16, the injection start timing is adjusted within the predetermined adjustment range. The fuel injection control device includes the program (an ignition timing detecting section: S72) for detecting the ignition timing concerning the injection performed at the injection start timing. The fuel injection control device includes the program (an adjustment range varying section: S72) for variably setting the adjustment range based on the ignition timing detected by the above program (the ignition timing detecting section). Thus, the timing of the injection centroid can be appropriately adjusted while maintaining the ignition timing within the appropriate range. As a result, reliable injection control can be realized.

(7) The program adopted as the program for detecting the above-described ignition timing obtains the time (i.e., the ignition delay) from the injection start to the ignition based on the injection execution timing (i.e., the injection start timing) and detects the ignition timing of the same injection based on the ignition delay. With such the construction, by using the predetermined map (FIG. 18) or the like, the above-described ignition timing can be detected relatively accurately and easily.

(8) The fuel injection control device includes the program (an injection centroid determining section: S71 of FIG. 16) for determining whether the deviation amount between the position of the actual injection centroid and the position of the injection centroid of the predetermined basic diagram is greater than the permissible level. In more detail, the program (the injection centroid determining section) performs the above determination based on whether the deviation amount between the maximum injection rate of the detected diagram and the maximum injection rate of the basic diagram is greater than the permissible level. In S72 of FIG. 16, when it is determined that the deviation amount of the position of the injection centroid is greater than the permissible level in S71, the injection command (the injection timing) to the injector 20 is varied such that the relative positional relationship between the injection centroid of the diagram as the actual profile of the injection rate transition and the injection centroid of the basic diagram becomes a relationship of as close timings between the injection centroids as possible. With such the construction, by performing the above-mentioned positional adjustment of the injection centroid only when the deviation amount of the position of the injection centroid is greater than the permissible level, the positional adjustment can be performed efficiently.

(9) The fuel injection control device includes the program (a basic diagram varying section: S12 of FIG. 4) for variably setting the basic diagram (i.e., the kind of the basic diagram) and the parameters of the basic diagram in accordance with the predetermined parameters (e.g., the fuel pressure, the engine rotation speed, the accelerator operation amount and the like acquired in S11 of FIG. 4). With such the construction, the parameters of the basic diagram can be varied in accordance with the situation of each time, and eventually, the above-described device can be realized in a more practical form.

(10) In S12 and S13 of FIG. 4, updating of the correction coefficients for the predetermined reference map, in which the injection command used when performing the injection control with the above-described injector 20 is written, is enabled. Thus, the injection command to the injector 20 can be varied. Accordingly, the injection command to the injector 20 can be varied easily and appropriately.

(11) The injection command to the injector 20 is produced such that the injection result (injection data) obtained based on the fuel pressure transition sensed during the present combustion cycle of the target engine is reflected in the injection in the subsequent combustion cycle. The production of the injection command is continuously performed while applying such the feedback to the injection command. Thus, appropriate fuel injection can be performed over a long time.

(12) The injector for performing the injection supply of the fuel to the target engine is the injector (injector 20) that has the fluid control valve (i.e., the outer valve 202 b) and the needle (needle 20 c). The fluid control valve controls the inflow of the fluid to the predetermined space (i.e., the oil pressure chamber Cd) and the outflow of the fluid from the same space. The needle (needle 20 c) performs reciprocation operation inside the valve body of the aforementioned injector in accordance with the pressure change of the oil pressure chamber Cd accompanying the inflow and the outflow of the fluid and opens/closes the fuel supply passage extending to the injection holes 20 f, thereby performing the valve opening/valve closing of the aforementioned injector. With such the fuel injection control device, appropriate fuel injection control can be performed by adjusting the injection characteristic of a general injector in accordance with the injection characteristic of each time without necessitating adoption of a special injector.

(13) The fuel injection control device according to the above-described embodiment is applied to the common rail type fuel injection system that has the common rail 12 and the fuel pressure sensor (the fuel pressure sensor 20 a). The common rail 12 accumulates the fuel to be supplied to the injector 20 under pressure. The fuel pressure sensor senses the pressure of the fuel flowing through the inside of the fuel passage (the pipe 14) extending from the common rail 12 to the fuel injection hole (the injection hole 20 f) of the injector 20 at the predetermined point downstream of the neighborhood of the fuel discharge hole of the common rail 12 with respect to the fuel flow direction in the fuel passage or more specifically at a point on the injector 20 side of the connection section 12 a (i.e., the orifice), or further specifically, at the fuel inlet of the injector 20 corresponding to a position closer to the fuel injection hole of the injector 20 than the common rail 12. In more detail, the fuel pressure sensor 20 a for sensing the fuel pressure is attached to the position closer to the fuel injection hole of the injector 20 than the common rail 12 in the pipe 14 connected to the fuel discharge side of the common rail 12. More specifically, the fuel pressure sensor 20 a is attached to the fuel inlet of the injector 20. In S21 of FIG. 5, the pressure of the fuel supplied to the injector 20 is sequentially sensed based on the output of the fuel pressure sensor 20 a. Thus, the pulsation pattern (surge characteristic or the like) indicating the injection characteristic at each time including the temporal characteristic change can be sensed with high accuracy. Eventually, the appropriate fuel injection control can be performed by appropriately adjusting the injection characteristic in accordance with the injection characteristic at each time.

(14) The fuel pressure sensor 20 a is provided on the injector 20 side of the connection section 12 a (the orifice). Therefore, the pressure fluctuation mode can be sensed with the fuel pressure sensor 20 a before the fuel pulsation is reduced by the orifice. Eventually, the pressure fluctuation mode can be sensed with high accuracy.

(15) A rail pressure sensor, which is generally attached to the common rail 12, is omitted in the above embodiment, so a wide space can be ensured near the common rail 12. With the structure having the above-described fuel pressure sensor 20 a, the usual fuel injection control can be performed appropriately based on the sensor output of the fuel pressure sensor 20 a even if the rail pressure sensor is omitted as described above.

(16) In the processing of FIG. 5, the sensor output of the above-described fuel pressure sensor 20 a is sequentially obtained at a relatively short interval, at which the profile of the pressure transition waveform can be created with the sensor output. Thus, the above-described pressure transition waveform (i.e., the pressure fluctuation mode) can be appropriately sensed with high accuracy.

(17) In the processing of FIG. 5, the sensor output of the above-described fuel pressure sensor 20 a is sequentially obtained at an interval of 20 μsec. Thus, the above-described pressure transition waveform (i.e., the pressure fluctuation mode) can be grasped appropriately.

(18) The fuel pressure sensor 20 a is provided to each one of the fuel inlets of the injectors 20 of the cylinders #1-#4. Thus, mountability and maintenance performance of each fuel pressure sensor 20 a are improved and the pressure can be sensed with high accuracy and relatively high stability.

The above embodiment may be modified as follows, for example.

In the above embodiment, both of the injection start timing and the injection end timing of the above-described injector 20 are adjusted at the predetermined ratio of 1:1 in S72 of FIG. 16. Alternatively, the both timings may be adjusted (moved) at another predetermined ratio such as a ratio of 3:7, a ratio of 1:9, or a ratio of 1:−1. In the case where the both timings are changed at the ratio other than 1:1, the diagram is deformed with the change of the timings. Therefore, the relationship between the adjustment ratio and the deformation mode of the diagram corresponding to the adjustment ratio may be prepared in the form of a map and the map may be used in the adjustment.

In the above-described embodiment, the orifice is provided in the connection section 12 a to reduce the pressure pulsation in the common rail 12. Alternatively, a flow damper (a fuel pulsation reducing device) may be provided in place of the orifice or together with the orifice to reduce the pressure pulsation in the common rail 12.

In the above-described embodiment, the sensing period and the stoppage period are set in the mode shown in FIG. 6 or 7. The present invention is not limited thereto but the sensing period or the stoppage period may be set in an arbitrary mode. The sensing period or the stoppage period may be set as a fixed value obtained through experiment or the like. Alternatively, the sensing period or the stoppage period may be set using a map or the like as a variable value corresponding to the situation of each time (specifically, the engine operation state). The stoppage period may be omitted if it is unnecessary.

The injection command to the above-described injector 20 may be corrected during one combustion cycle. For example, the fuel injection control device may include a program that uses a pressure transition sensed until the present time based on the fuel pressure transition sequentially sensed by the processing of S21 of FIG. 5 in a combustion cycle of the target engine to correct the injection command to the injector 20 (for example, the energization period (pulse width) of the injector 20) about a predetermined operation concerning the fuel injection of the injector 20 to be performed after the present time in the same cycle. Thus, in accordance with an error in the area of the detected diagram (i.e., the injection quantity) up to the time, the injection command (for example, a valve-closing command) of the injector 20 concerning the operation after the time can be adjusted. Eventually, the injection quantity error resulting from the deviation in the area of the detected diagram can be compensated to maintain the fuel injection quantity at the time to be appropriate.

In the above-described embodiment, adoption of the adaptation map (used in S12 of FIG. 4), whose adaptation values are decided beforehand through the experimentation or the like, is supposed, and the correction coefficient for correcting the injection characteristic based on the adaptation map is updated. Alternatively, in place of the correction coefficient, the corrected value (i.e., a value reflecting the correction coefficient) may be stored in the EEPROM or the like. If the corrected value has sufficient reliability with such construction, a construction not requiring the above-described adaptation map, i.e., an adaptation-less construction, can be adopted.

In the above embodiment, only the injection centroid is adjusted among the parameters of the diagram as the profile of the injection rate transition. Alternatively, it is also effective to adjust the maximum injection rate (the injection rate at the time when the injection rate is maximized during the same injection) in addition to the injection centroid. FIG. 19 is a flowchart showing an example of such the configuration. That is, in this example, in place of the processing of FIG. 16, processing shown in FIG. 19 is performed. Thus, after the timing of the injection centroid of the diagram as the profile of the injection rate transition is adjusted (S82), the maximum injection rate Rmax is further adjusted (S83).

As shown in FIG. 19, in a series of the processing, processing similar to the processing of S71 and S72 of FIG. 16 is performed in S81 and S82 of FIG. 19. That is, first in S81 and S82, deviation determination of the maximum injection rate Rmax and adjustment of the injection centroid are performed. After the adjustment of the injection centroid in the S82, adjustment of the maximum injection rate Rmax is further performed in following S83. Thus, the injection centroid of the detected diagram (eventually, actual injection centroid) is approximated to the injection centroid of the basic diagram not only in the direction of the timing but also in the direction of the injection rate. Eventually, the more suitable torque control and emission control are realized.

The adjustment of the injection rate (the maximum injection rate, and eventually, the injection rate at the injection centroid) can be performed by adjusting a predetermined fuel pressure parameter such as pressure in the common rail 12 or eventual injection pressure (equivalent to one of injection conditions of the injector). This scheme uses a relationship that the maximum injection rate increases as the injection pressure increases.

For example, the pressure in the common rail 12 can be varied by varying the pumping quantity of the fuel pump 11 that pumps and supplies the fuel to the injector 20, or more specifically, by adjusting the drive current amount of the suction control valve 11 c (shown in FIG. 1). The rising and falling speed of the injection rate and the maximum injection rate are increased by increasing the pumping quantity of the fuel pump 11, for example.

Alternatively, the pressure in the common rail 12 may be varied by providing a pressure reducing valve in the injector 20 or in a fuel supply passage of the injector 20 (for example, in the common rail 12) and by varying the valve opening degree of the pressure reducing valve. The rising and falling speed of the injection rate and the maximum injection rate are decreased by increasing the valve opening degree of the pressure reducing valve.

The pressure in the common rail 12 can be varied by varying the pumping timing of the fuel pump 11 that pumps and supplies the fuel to the injector 20. FIG. 20 is a time chart showing an example of the pressure variation mode. In order to approximate fuel pumping timing t201 of the fuel pump 11 to the injection start timing, for example, the timing t201 is changed to timing t202 shown in FIG. 20. By bringing the pumping timing of the fuel pump close to the injection start timing in this way, the pressure transition P (i.e., the actual measurement value measured by the fuel pressure sensor 20 a) changes from a solid line L201 to a broken line L202, and the injection rate transition R changes from a solid line L201 a to a broken line L202 a as shown in FIG. 20 respectively. Eventually, the rising and falling speed of the injection rate R and the maximum injection rate increase.

When an injector having multiple types of switchable injection holes (for example, multiple injection holes having different shapes) is adopted as an injector that injects and supplies the fuel to the target engine, the injection pressure of the injector may be varied by switching the injection holes. When the injector has a pressure intensifying mechanism, the injection pressure of the injector may be varied by operating the pressure intensifying mechanism.

Furthermore, an injector adopted as an injector that performs injection supply of the fuel to the target engine may have a needle, which performs valve opening and valve closing of the injector by opening and closing (blocking) an injection hole (equivalent to a fuel injection hole) or a fuel supply passage extending to the injection hole based on a predetermined reciprocating operation of the needle inside a valve body, and may continuously vary an amount of the reciprocating motion of the needle in accordance with an injection command to the injector. In such the case, a diagram as a profile of an injection rate transition can be variably controlled with a high degree of freedom through the injection command to the aforementioned injector.

FIG. 21 shows an example of a structure of the injector of this kind, i.e., a direct acting piezo injector.

As shown in FIG. 21, for example, the injector has a piezoelectric element 103 consisting of a laminated body (a piezo stack) of a piezoelectric material such as PZT as a drive device (actuator) that directly drives a needle 102, which performs valve opening and valve closing of the aforementioned injector (in more detail, an injection hole 101). That is, the piezoelectric element 103 is energized when the injection is performed with the injector. If the energization to the piezoelectric element 103 is started to perform the fuel injection, a piezo piston 104 is displaced toward an injector tip end side (i.e., toward the injection hole 101 side) with the extension of the piezoelectric element 103. Thus, fuel pressure in a second oil-tight chamber 105, a transmission passage 106 and a first oil-tight chamber 107 increases. Eventually, a force of the fuel in the first oil-tight chamber 107 to push a needle stopper 109 toward an injector rear side increases. If summation of the force of the fuel in the first oil-tight chamber 107 to push the needle stopper 109 toward the injector rear side and a force of the high-pressure fuel in a needle chamber 108 to push the needle 102 toward the injector rear side exceeds summation of a force of a spring 110 and low-pressure fuel to push the needle stopper 109 toward the injector tip end side and a force of high-pressure fuel in a balance chamber 111 to push a back side of a balance piston 112 toward the injector tip side, the needle 102 is displaced toward the injector rear side and the aforementioned injector opens. Thus, the fuel inside the injector is injected to an outside through the injection hole 101.

If electric discharge of the piezoelectric element 103 is started, the piezo piston 104 is displaced toward the injector rear side with contraction of the piezoelectric element 103. Accordingly, the fuel pressure in the second oil-tight chamber 105, the transmission passage 106, and the first oil-tight chamber 107 falls. Eventually, the force of the fuel in the first oil-tight chamber 107 to push the needle stopper 109 toward the injector rear side decreases. If summation of the force of the fuel in the first oil-tight chamber 107 to push the needle stopper 109 toward the injector rear side and the force of the high-pressure fuel in the needle chamber 108 to push the needle 102 toward the injector rear side falls below summation of the force of the spring 110 and the low-pressure fuel to push the needle stopper 109 toward the injector tip end side and the force of the high-pressure fuel in the balance chamber 111 to push the back side of the balance piston 112 toward the injector tip end side, a force directed toward the injector tip end side is applied to the needle 102 and the piezo injector is closed. Thus, the fuel injection ends.

In this injector, a displacement amount of the needle 102 (i.e., a reciprocation movement amount) toward the injector rear side, i.e., a lift amount, changes continuously in accordance with a displacement amount of the piezoelectric element 103, and eventually, in accordance with the injection command to the aforementioned injector (i.e., an energization amount of the piezoelectric element 103). The lift amount is proportional to the displacement amount of the piezoelectric element 103, for example. Therefore, the lift amount can be arbitrarily controlled from a zero lift amount corresponding to the valve-closing of the aforementioned injector to a full lift amount as the maximum lift amount. That is, when such the direct acting injector is adopted, the injection rate and the timing at the actual injection centroid can be approximated to the injection rate and the timing at the injection centroid of the reference diagram respectively based on the injection command to the injector (i.e., voltage signal to the piezoelectric element 103).

Moreover it is also effective to adjust only the maximum injection rate without detecting the injection centroid according to the use or the like. It is also effective to select one out of the injection centroid and the maximum injection rate of the diagram as the profile of the injection rate transition as a target of the adjustment at the time based on the injection centroid and the maximum injection rate sensed at the time and to adjust the selected adjustment target (the position of the injection centroid or the maximum injection rate) by variably setting the injection command to the injector 20 or the injection condition of the injector 20.

In the case of the multi-injection, such the estimation and the adjustment of the injection rate characteristic (the fluctuation mode of the injection rate) is not limited to the main injection but may be performed also for an injection performed before or after the main injection (for example, the pilot injection or the post-injection).

The above-described basic diagram may be an arbitrary diagram. A diagram such as a diagram in a parabolic shape as shown in FIG. 22A, a diagram in a triangular shape as shown in FIG. 22B, a diagram in a quadrilateral shape as shown in FIG. 22C, or a diagram in a trapezoidal shape as shown in FIG. 22D may be employed as the above-mentioned basic diagram. A point G in each diagram shows the centroid of each diagram.

In order to provide a highly practical construction reflecting characteristics of a general injector it is effective to adopt one of a triangle, a trapezoid and a rectangle or a diagram made by combining multiplicity of at least one kind of the triangle, the trapezoid and the rectangle as the basic diagram. That is, in addition to the triangle (FIG. 22B) or the trapezoid (FIG. 22D), a boot-shaped diagram made by combining two trapezoids as shown in FIG. 23A or a diagram made by combining trapezoids and rectangles in a more complicated manner as shown in FIG. 23B may be adopted as the basic diagram mentioned above.

In the above-described embodiment, the diagram as the profile of the injection rate transition is detected at each time and the diagram as the actual profile of the injection rate transition is turned into the diagram belonging to the basic diagram. Alternatively, the positions of the centroids of the diagrams may be matched (coincided or approximated) with each other while leaving the detected diagram to be the diagram different from the basic diagram. That is, when the actual diagram (the detected diagram) is the triangle and the basic diagram is the trapezoid, the positions of the centroids of the triangle and the trapezoid may be matched without performing the adjustment of the diagram (i.e., the adjustment for turning the triangle into the trapezoid).

An inflection point of the pressure transition may be obtained as a starting point of steep pressure rising, in which a pressure change amount per unit time exceeds a predetermined level, or for example, as timing at which a second order differential value ddP of the fuel pressure P acquired through the processing of S23 of FIG. 5 shifts from a smaller side than a predetermined threshold value to a larger side than the predetermined threshold value. Then, the timing (the timing t3) when the injection rate R starts decreasing after reaching the maximum injection rate of the above-described injector 20 may be detected based on the pressure inflection point (refer to part (d) of FIG. 9). Thus, the timing t3 can be detected appropriately.

In the above-described embodiment, the fuel pressure sensor 20 a for sensing the fuel pressure is attached to the fuel inlet of the above-described injector 20. Alternatively, the fuel pressure sensor 20 a may be provided inside the injector 20 (for example, near the injection hole 20 f shown in FIG. 2). An arbitrary number of the fuel pressure sensor(s) may be used. For example, two or more sensors may be provided to the fuel flow passage of one cylinder. In the above-described embodiment, the fuel pressure sensor 20 a is provided to each cylinder. Alternatively, the sensor(s) may be provided only in a part of the cylinders (for example, one cylinder), and an estimate based on the sensor output may be used for the other cylinder(s).

In the above-described embodiment, the cylinder pressure sensor 53 is provided to each cylinder. Alternatively, the sensor(s) may be provided only in a part of the cylinders (for example, one cylinder). In the case where the cylinder pressure sensor(s) is/are provided only in a part of the cylinders in this way without providing the sensor(s) in the other cylinder(s), it is effective to use a configuration of estimating the cylinder pressure of the other cylinder(s) using the actual measurement value of the cylinder pressure obtained in the cylinder(s) provided with the cylinder pressure sensor(s). Thus, the cylinder pressure of many cylinders can be measured while minimizing the number of the sensor(s) and a computation load. Moreover, the injection characteristics (the injection quantity and the like) can be controlled with high accuracy based on the measurement value. The cylinder pressure sensor 53 may be omitted if it is unnecessary.

In the above-described embodiment, the sensor output of the above-described fuel pressure sensor 20 a is sequentially acquired at an interval (i.e., in a cycle) of 20 μsec. The acquisition interval may be arbitrarily changed in a range capable of grasping the tendency of the pressure fluctuation mentioned above. However, according to the experiment performed by the inventors, an interval shorter than 50 μsec is effective.

It is also effective to provide a rail pressure sensor for measuring the pressure in the common rail 12 in addition to the above-described fuel pressure sensor 20 a. With such the construction, the pressure in the common rail 12 (the rail pressure) can be acquired in addition to the pressure measurement value obtained by the above-described fuel pressure sensor 20 a. As a result, the fuel pressure can be sensed with higher accuracy.

The kind and the system configuration of the engine as the control target can also be arbitrarily modified in accordance with the use and the like.

In the above embodiment, the present invention is applied to the diesel engine as an example. However, fundamentally, the present invention can be also applied to a spark ignition gasoline engine (specifically, a direct-injection engine) and the like in the similar way. For example, a fuel injection system of a direct injection gasoline engine generally has a delivery pipe that stores fuel (gasoline) in a high-pressure state. In the system, the fuel is pumped from a fuel pump to the delivery pipe, and the high-pressure fuel in the delivery pipe is injected and supplied into an engine combustion chamber through an injector. The present invention can be applied also to such the system. In this system, the delivery pipe corresponds to the pressure accumulator.

The device and the system according to the present invention can be applied not only to the injector that injects the fuel directly into the cylinder but also to an injector that injects the fuel to an intake passage or an exhaust passage of the engine in order to control the fuel injection characteristic of the injector or the like. Moreover, the target injector is not limited to the injector illustrated in FIG. 2 but is arbitrary. For example, an injector that opens/closes an injection hole with a needle or an injector of an outward valve opening type may be employed. When such the change of the construction is applied to the above-described embodiment, it is desirable to appropriately change the details of the various kinds of processing (programs) mentioned above into the optimum form in accordance with actual construction (as design change) as needed.

In the above embodiment and the modifications, it is assumed that various kinds of software (programs) are used. Alternatively, similar functions may be realized by hardware such as dedicated circuits.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 

1. A fuel injection control device for a fuel supply system that injects fuel to an inside of a cylinder as a part of a target engine for performing fuel combustion, an intake passage of the engine or an exhaust passage of the engine with a predetermined injector, the fuel injection control device comprising: a fuel pressure sensing means for sequentially sensing fuel pressure fluctuating with the injection of the injector; an injection centroid detecting means for detecting an injection centroid as a geometric centroid of a diagram as a profile of a transition of an injection rate at a present time based on a transition of the fuel pressure sequentially sensed by the fuel pressure sensing means, the injection rate being equivalent to a fuel quantity injected from the injector per unit time; and an injection varying means for varying an injection command to the injector or an injection condition of the injector based on the injection centroid detected by the injection centroid detecting means and an injection centroid of a predetermined basic diagram such that a relative positional relationship between the injection centroid of the diagram as the actual profile of the injection rate transition and the injection centroid of the basic diagram becomes a predetermined relationship.
 2. The fuel injection control device as in claim 1, wherein the injection varying means varies the injection command to the injector or the injection condition of the injector to approximate timings of the injection centroids of the diagram as the actual profile of the injection rate transition and the basic diagram to each other.
 3. The fuel injection control device as in claim 2, wherein the injection varying means adjusts at least one of injection start timing and injection end timing of the injector by varying the injection command to the injector or the injection condition of the injector, thereby approximating the timings of the injection centroids of the diagram as the actual profile of the injection rate transition and the basic diagram to each other.
 4. The fuel injection control device as in claim 3, wherein the injection varying means adjusts both of the injection start timing and the injection end timing of the injector at a predetermined ratio therebetween.
 5. The fuel injection control device as in claim 3, wherein the injection varying means adjusts the injection start timing within a predetermined adjustment range, the fuel injection control device further comprising: an ignition timing detecting means for detecting ignition timing concerning the injection performed at the injection start timing; and an adjustment range varying means for variably setting the adjustment range based on the ignition timing detected by the ignition timing detecting means.
 6. The fuel injection control device as in claim 5, wherein the ignition timing detecting means obtains a time from the injection start to the ignition based on the injection start timing as an ignition delay and detects the ignition timing of the same injection based on the ignition delay.
 7. The fuel injection control device as in claim 1, wherein the injection varying means varies the injection command to the injector or the injection condition of the injector to approximate values of the injection rates at the injection centroids of the diagram as the actual profile of the injection rate transition and the basic diagram to each other.
 8. The fuel injection control device as in claim 7, wherein the injection varying means varies injection pressure of the injector as the injection condition.
 9. The fuel injection control device as in claim 8, wherein the injection varying means varies the injection pressure of the injector by varying a pumping quantity of a fuel pump that performs pumping supply of the fuel to the injector.
 10. The fuel injection control device as in claim 8, wherein the injection varying means varies the injection pressure of the injector by varying pumping timing of a fuel pump that performs pumping supply of the fuel to the injector.
 11. The fuel injection control device as in claim 8, wherein the injection varying means varies the injection pressure of the injector by varying a valve opening degree of a pressure reducing valve provided to the injector or to a fuel supply passage of the injector.
 12. The fuel injection control device as in claim 1, further comprising: an injection centroid determining means for determining whether a deviation amount between a position of the actual injection centroid and a position of the injection centroid of the predetermined basic diagram is greater than a permissible level, wherein when the injection centroid determining means determines that the deviation amount between the positions of the injection centroids is greater than the permissible level, the injection varying means varies the injection command to the injector or the injection condition of the injector such that a relative positional relationship between the injection centroids of the diagram as the actual profile of the injection rate transition and the basic diagram becomes a predetermined relationship.
 13. The fuel injection control device as in claim 12, further comprising: a maximum injection rate sensing means for sensing an injection rate at the time when the injection rate is maximized in the injection based on the transition of the fuel pressure sequentially sensed by the fuel pressure sensing means, the injection rate being equivalent to a fuel quantity injected from the injector per unit time, wherein the injection centroid determining means determines whether the deviation amount between the injection centroids of the both diagrams is greater than the permissible level based on whether a deviation amount between the maximum injection rate sensed by the maximum injection rate sensing means and the maximum injection rate of the basic diagram is greater than another permissible level.
 14. The fuel injection control device as in claim 1, wherein the basic diagram includes one of a triangle, a trapezoid and a rectangle or a diagram made by combining multiple pieces of at least one kind of the triangle, the trapezoid and the rectangle.
 15. The fuel injection control device as in claim 1, further comprising: a basic diagram varying means for variably setting at least one of the basic diagram and a parameter of the basic diagram in accordance with a predetermined parameter.
 16. The fuel injection control device as in claim 1, wherein the injection varying means varies the injection command to the injector by updating a correction coefficient of a predetermined reference map, in which the injection command used when the injection control is performed with the injector is written.
 17. The fuel injection control device as in claim 1, wherein the injection varying means produces the injection command to the injector such that an injection result obtained based on the fuel pressure transition sequentially sensed with the fuel pressure sensing means during a present combustion cycle of the target engine is reflected in an injection in a subsequent combustion cycle.
 18. The fuel injection control device as in claim 1, wherein the injection varying means uses a pressure transition sensed up to the present time in a combustion cycle of the target engine based on the fuel pressure transition sequentially sensed by the fuel pressure sensing means to produce the injection command to the injector about a predetermined operation concerning the fuel injection of the injector to be performed after the present time in the same cycle.
 19. The fuel injection control device as in claim 1 wherein the injector has a fluid control valve for controlling an inflow of a fluid to a predetermined space and an outflow of the fluid from the same space and a needle that performs reciprocation operation inside a valve body of the injector in accordance with a change in pressure in the space accompanying the inflow and the outflow of the fluid to open and close an injection hole or a fuel supply passage extending to the injection hole, thereby performing valve opening and valve closing of the injector.
 20. The fuel injection control device as in claim 1, wherein the injector has a needle that performs predetermined reciprocation operation inside a valve body of the injector to open and close an injection hole or a fuel supply passage extending to the injection hole, thereby performing valve opening and valve closing of the injector, and the injector continuously varies a reciprocation movement amount of the needle in accordance with the injection command to the injector.
 21. The fuel injection control device as in claim 1, wherein the fuel supply system is a pressure accumulation fuel injection system that has a pressure accumulator for accumulating the fuel to be supplied to the injector under pressure and at least one fuel pressure sensor for sensing pressure of the fuel flowing through an inside of a fuel passage extending from the pressure accumulator to a fuel injection hole of the injector at a predetermined point downstream of a neighborhood of a fuel discharge hole of the pressure accumulator with respect to a fuel flow direction, and the fuel pressure sensing means sequentially senses the fuel pressure based on an at least one output of the at least one fuel pressure sensor.
 22. The fuel injection control device as in claim 21, wherein at least one of the fuel pressure sensors is provided inside the injector or near the injector.
 23. The fuel injection control device as in claim 21, wherein at least one of the fuel pressure sensors is provided at a position in a fuel discharge pipe of the pressure accumulator closer to the fuel injection hole of the injector than the pressure accumulator.
 24. The fuel injection control device as in claim 21, wherein the fuel pressure sensing means sequentially obtains a sensor output of the fuel pressure sensor at an interval short enough to create a profile of a pressure transition waveform with the sensor output.
 25. The fuel injection control device as in claim 21, wherein the fuel pressure sensing means sequentially obtains the sensor output of the fuel pressure sensor at an interval shorter than 50 microseconds.
 26. The fuel injection control device as in claim 1, wherein the fuel supply system is a fuel injection system that has a pressure accumulator for accumulating the fuel to be supplied to the injector under pressure, a fuel pulsation reducing means provided in a connection section between the pressure accumulator and a fuel discharge pipe of the pressure accumulator for reducing a fuel pulsation transmitted to the pressure accumulator through the fuel discharge pipe, and at least one fuel pressure sensor for sensing pressure of the fuel flowing through an inside of a fuel passage extending from the pressure accumulator to a fuel injection hole of the injector at a predetermined point downstream of the fuel pulsation reducing means with respect to a fuel flow direction, and the fuel pressure sensing means sequentially senses the fuel pressure based on at least one output of the at least one fuel pressure sensor.
 27. The fuel injection control device as in claim 26, wherein the fuel pulsation reducing means is constituted by an orifice, a flow dampen or a combination of the orifice and the flow damper.
 28. The fuel injection control device as in claim 26, wherein at least one of the fuel pressure sensors is provided inside the injector or near the injector.
 29. The fuel injection control device as in claim 26, wherein at least one of the fuel pressure sensors is provided at a position in a fuel discharge pipe of the pressure accumulator closer to the fuel injection hole of the injector than the pressure accumulator.
 30. The fuel injection control device as in claim 26, wherein the fuel pressure sensing means sequentially obtains a sensor output of the fuel pressure sensor at an interval short enough to create a profile of a pressure transition waveform with the sensor output.
 31. The fuel injection control device as in claim 26, wherein the fuel pressure sensing means sequentially obtains the sensor output of the fuel pressure sensor at an interval shorter than 50 microseconds.
 32. A fuel injection control device for a fuel supply system that injects fuel to an inside of a cylinder as a part of a target engine for performing fuel combustion, an intake passage of the engine or an exhaust passage of the engine with a predetermined injector, the fuel injection control device comprising: a fuel pressure sensing means for sequentially sensing fuel pressure fluctuating with the injection of the injector; a maximum injection rate sensing means for sensing an injection rate at the time when the injection rate is maximized in the injection based on a transition of the fuel pressure sequentially sensed by the fuel pressure sensing means the injection rate being equivalent to a fuel quantity injected from the injector per unit time; and an injection varying means for varying an injection command to the injector or an injection condition of the injector based on the maximum injection rate sensed by the maximum injection rate sensing means to approximate the maximum injection rate of the actual injection to a predetermined reference value.
 33. A fuel injection control device for a fuel supply system that injects fuel to an inside of a cylinder as a part of a target engine for performing fuel combustion, an intake passage of the engine or an exhaust passage of the engine with a predetermined injector, the fuel injection control device comprising: a fuel pressure sensing means for sequentially sensing fuel pressure fluctuating with the injection of the injector; an injection centroid detecting means for detecting an injection centroid as a geometric centroid of a diagram as a profile of a transition of an injection rate at a present time based on a transition of the fuel pressure sequentially sensed by the fuel pressure sensing means, the injection rate being equivalent to a fuel quantity injected from the injector per unit time; a maximum injection rate sensing means for sensing an injection rate at the time when the injection rate is maximized in the injection based on a transition of the fuel pressure sequentially sensed by the fuel pressure sensing means the injection rate being equivalent to a fuel quantity injected from the injector per unit time; and an injection varying means for adjusting at least one of the injection centroid of the diagram as the actual profile of the injection rate transition and the maximum injection rate of the actual injection by variably setting the injection command to the injector or the injection condition of the injector based on the injection centroid detected by the injection centroid detecting means and the maximum injection rate sensed by the maximum injection rate sensing means.
 34. The fuel injection control device as in claim 33 wherein the injection varying means adjusts one of the injection centroid of the diagram as the actual profile of the injection rate transition and the maximum injection rate of the actual injection and then adjusts the other one.
 35. The fuel injection control device as in claim 33, wherein the injection varying means selects one of the injection centroid of the diagram as the actual profile of the injection rate transition and the maximum injection rate of the actual injection as an adjustment target at the present time based on the injection centroid detected by the injection centroid detecting means and the maximum injection rate sensed by the maximum injection rate sensing means and adjusts the one selected as the adjustment target by variably setting the injection command to the injector or the injection condition of the injector. 